Go with Apple and Flutters, the path is longer and they might need your help along the way. Especially with Fluttershy K.O.ed like she is. 
Go with AJ and Fluttershy.
You feel sorry for the yellow pegasus. You decide to risk it with Applejack and follow the small group.
Follow aj and fluttershy.
Flutters and Applejack
Go with Apple and Flutters, the path is longer and they might need your help along the way. Especially with Fluttershy K.O.ed like she is.
Deciding to use logic and deduction like your hero, Sherclop Holmes (note to self, read other Sherclop books in your free time), you reason that going with the larger group of four mares would be downright suicidal. Also, you deduce that the yellow pegasus is definitely as scared as you are (if not more so which you didn't even think was possible) and could possibly be a future help.
You decide to follow Applejack and the yellow pegasus. Not only is it smaller then the other group so there's less chance of you getting caught, but there's also the fact of how the yellow pegasus is acting. You decide to try and use logic and deduction like one of your hero, Sherclop Holmes. You somehow manege to deduce that the yellow pegasus is definitely as scared as you are, if not more so, which you didn't even think was possible. You also make a mental note to self, to read the other Sherclop books in your free time. You are about to follow them when a thought cross your mind...
...Wait a second,
"Don't you remember Twi? You cast a spell on me after the wedding. You said it would only*yawn* work on me since I was the Element of Honesty, and a disguise is kind of like a lie. The spell gives me this twitch on mah back whenever a changeling is around," she tells you and then...immediately falls back asleep.
The way this was phrased makes me think that AJ's detection thing only works when a changeling is in disguise. Perhaps it would be a good idea to drop our current disguise because we are not intending to interact with anybody directly and having it on will only set off AJ's changeling sense. It is not like it takes all that long to get a disguise up and running anyway.
You remember how Applejack described the spell Twilight put on her.
"Don't you remember Twi? You cast a spell on me after the wedding. You said it would only*yawn* work on me since I was the Element of Honesty, and a disguise is kind of like a lie. The spell gives me this twitch on mah back whenever a changeling is around."
The why that was worded makes you think the spell could only work when you are disguised, but you quickly shake off the thought There's no telling if that's how the spell work's. You think to yourself in a serious, Besides it's to late to see if that's true or not, if I do release my disguise now then the mares would see the flash from the spell. You then notice that the mares are moving out again, so with a silent jump (somehow) you begin to follow be hide Applejack and the yellow pegasus.
12 MINUTES LATER
You follow the smaller group and help them in subtle (and often painful (to you)) ways,
For the past twelve minutes you've been secretly helping Applejack and the yellow pegasus get though the alternate path up the mountain. You've learned three things because of this, one is that the yellow pegasus is scared of EVERY LITTLE THING! You don't what to sound mean, but because of her false alarm screams of fright, almost all bruises you got were from them. Two, the two mares your following are very danger prone. All the things that you stop from happening to the two mares had only happened when they got close to them. Heck, one of the things that happened was a boulder almost flatten them, but get this. You went ahead of them to see if anything nearby was dangerous. You saw the boulder and decide to test its sturdiness, you pushed and pulled the thing with your magic and it didn't even budge by a inch. Yet when the two mares walk under it, the stinking thing begins to fall right on top of them! Luckily for them you used your magic to pull it away from them. Sadly, you use to much magic in your panic to save the mares, so the boulder smacked right into you because of that. Your horn is now to inches smaller now thanks to that.
Finally, You really, really, really hate Lady Luck. You thought you had bad luck, but these mares have even more terrible luck then you! You didn't even think that was possible. You just thank Luna's moon that no wild animals have po*growl* OH FOR THE LOVE OF LUNA! You look over from your hiding spot, another tree, to see a mountain lion walking towards the two ponies. For some reason Applejack is the only one who is scared, and the yellow pegasus isn't scared at all. Which shocks you considering the yellow pegasus, from what you've seen, is scared of everything. Your about to use your magic to scare away the mountain lion, when you see the most unbelievable thing ever.
The yellow pegasus is cuddling the mountain lion, and the mountain lion is purring...
The yellow pegasus, the same yellow pegasus who's scared of literally everything, is hugging a wild, predatory, animal...
....
....
....
*crack* That's the sound of your brain breaking...again! Your jaw drops to the ground, no literary its just hanging from your mouth on the ground. You do what everyling does when they see something that shouldn't be possible...you faint.
10 MINUTES LATER
You wake up awhile later to see that somehow you manege to hold onto the branch of the tree you are on even though you fainted. You look around to see that Applejack and the yellow pegasus are both gone. You begin to panic, thinking that you lost them and that you were stranded on this mountain forever. Or worse, they could have been eaten by that mountain lion, and you could have saved them, but you fainted because of something very immature and it will be all your fault. OH LUNA, WHAT HAVE I DONE. WHAT AM I GONNA TELL THERE FAMILY'S. OH NO, WHAT AM I GONNA TELL APPLEBLOOM. I'M DOOMED, DOOMED I SA*slap*. You slap yourself to calm yourself down when you see there tracts. You sigh in relief and say out loud "Oh thank goodness, there alive...I hope." You begin to stealthily follow the tracts.
12 MINUTES LATER
You finally make it to were the two mares went to. You see that they have caught up with the others and are talking about something. You look at the ground to see...a billion sets of tik-tak-toe? Whoever played X's must really stink at playing, cause they lost every time. You think to yourself while holding back your laughter so that you don't get caught. You notice that they are continuing going up the mountain. You are about to follow them when you see a other path that looks like a shortcut up the mountain. You decide to take....
Which path do you take?