For about twenty years, Rarity suffered a debilitating mental illness that made her forget many things. Her friends took notice and tried to get her to see a doctor, but she was stubborn. By the time she relented, it was too late; it had progressed past the point of curability. Over time, she couldn't remember anything new, and began to forget things she had learned.
Her death came as a sort of relief to Applejack and Twilight. She died in her sleep due to a stroke, only nine months after Rainbow Dash.
The funeral was a sad affair. Her daughter setting it up at the expense of her customers. She had decided to have it set in Ponyville, much to the chagrin of most of Rarity's previous acquaintances. Applejack was glad that she didn't need to travel so far.
"Well, looks like its just you and me, Twi," stated Applejack as she and Twilight walked away from the funeral.
Twilight hung her head before commenting "Well, you seem to be doing well. How is your family?"
"Doin' good. About to have my first great-grandbaby in a few months. How's your-oop! Sorry, Ah didn't mean…"
"That's okay," Twilight sighed. "Rainbow Dash, right before she died, was pining for a family. Me? I guess I don't know. It would be nice, but raising fillies? I don't think I could do that."
"Ah didn't think I'd be able to raise my own fillies, but Ah found out you have to be stern, yet caring. Now Ah admit Ah had some experience with Apple Bloom, but Rarity had her parents to look after Sweetie Belle. She raised her daughter just fine. Ah'm sure you could manage it with your smarts," Applejack smiled.
Twilight pondered at this a bit before her mind latched on something else. "Did you notice that Rarity's daughter seemed a little distant?"
Applejack nodded before noticing this as well. "Oh my stars… just like Rarity before she… We have to get her to the Doc! We…"
"Applejack, calm down!" Twilight ordered. "Don't worry, I'll get her to the doctor, even if I have to drag her there. I just hope it's not too late," she bemoaned.
Applejack put on a worried smile and continued to walk with her friend. They walked in silence for a few minutes, just enjoying each other's company.
"Well, you're looking good for being over eighty," Twilight smiled.
"You're not looking bad yourself, Twi," Applejack joked. Twilight just groaned, rolling her eyes. "What's the matter, Twi?"
"Do you know how many people have said that?" she shook her head. "It's getting annoying. I didn't choose to not age! I didn't choose to watch my friends die! I didn't…" Twilight started to rant.
"Whoa there, Twilight! Ah think you need to take a breather," Applejack shied away.
Twilight looked at AJ, shut her eyes, then groaned in utter frustration. She sighed, tiredly looking her friend. "I'm sorry. It's just… I don't know. I've heard it just too many times. Even the older professors have noticed. I just," she sighed, "it seems that I'm not normal; it bugs me to no end."
Applejack nuzzled Twilight. "Don't worry sugarcube. Ah'm still here fer you. Just pop in fer a visit and we'll talk. Ah could always use the company."
Twilight smiled sadly. "Yes, that would be nice." I wonder how long we'll be together.