Nice!

and a foal is conceived a vary loving addition to a good story.
I prefer having a clop as a side story from the mane as this way it does not distract from the mane story.

up to chest - up to her chest
the guard asked - the guards asked
fake suck at her - fake suckle at her
This was all things - These were all things
Penny before, the unicorn - Penny before. The unicorn
that is why she - that was why she
Same green mane - You mentioned this in the previous sentence.
against her, rippling running - against her, ripples running
slow, she made sure - slow, she had made sure
your wonton display - your wanton display
*****
This was intense, but given that it resulted in the conception of their foal, that's kind of expected. The added intimacy lends more depth and warmth to their characters and flows naturally with the existing narrative without being a distraction or feeling out of place or forced.

7026382 It was both of their first times. Stick had seen other changelings have sex with ponies, in the early days of the Canterlot hive, and her job in Chrysalis' hive was to tend the breeders, so I figure she knew the ins and outs of the process. But for both of them, this was a very special time. It was meant to be intense, a very stark comparison to Jenny and Sablee's romp, they were just two experienced adults having some fun.

She ignored it, it was easy to now her brain had two things backing it up.

Not sure what you wanted to do here.

7103233 Think I got it a bit better explained. Thanks again

7103242 Much clearer now.

Penny remembered what the rogue changelings had done, suddenly wondering if Stick would have even tried her own mental fangs if she hadn't had that happen. "It can hurt, if they are mean about it. Stick would never do anything to hurt me, or anypony."

... without due cause, that is.