As we know, Miss Twilight Sparkle did not attend the birthdayparty of Miss Moon Dancer. The next day, Miss Twilight Sparkle moved to Ponyville. Only 4 of her 5 friends attended the birthdayparty of Miss Moon Dancer. It is likely that Miss Moon Dancer had a crush on Miss Twilight Sparkle. This is counterfactual so we can never know, but it seems that Miss Twilight Sparkle would have turned down Miss Moon Dancer, if she would have attened the birthdayparty of Miss Moon Dancer the night before going of to Ponyville. Miss Moon Dancer could have taken the rejection very badly. Miss Moon Dancer might have become a recluse anyway:

Miss Twilight Sparkle liked her friends in Canterlot, but was not very strongly attached to them. As for sexual/romantic-interest, Miss Twilight Sparkle has only ever shown interest in the male ape Mister Flash Sentry:

I imagine this conversation between Miss Fluttershy and Princess Twilight Sparkle:

Princess Twilight Sparkle:
"I hear that you can a gibbon rescued from being a pet."

Miss Fluttershy:
"I do."

Princess Twilight Sparkle:
"¿Could I meet him?"

Miss Fluttershy:
"You cannot meet her because she is in isolation. She need to recover from the stress."

Princess Twilight Sparkle:
"After she recovers, ¿then could I meet her?"'

Miss Fluttershy:
"Over the years, I encountered 4 ponies with your liking animals like you do. You should not feel ashamed for feelings you cannot control, but always remember that it is a decision to act on those feelings and that when you act on those feelings you hurt animals. Help is available."

Princess Twilight Sparkle:
"I do not know what you mean."

Miss Fluttershy:
"The 1st step to solving your problem is admitting that you have a problem. I have brochures back in my cottage."

Princess Twilight Sparkle:
"!I do not have a problem!"

Miss Fluttershy:
"Please take and read the brochure anyway."

Princess Twilight Sparkle:
"Okay."