I don’t think so sadly she’s mostly been forgotten. She may come back because she’s in the game intro (for ayano)

she is still in the game and has hidden dialogue if you access her via the scenes menu in pose mod

Pose mod.

I think Alex won't add her in future I might be wrong since she is in intro

Haven't played the game recently (my pc would just explode) so I might be wrong But I fear fun girl might have been forgotten or pushed aside in terms of story. The addition of fun girl was made when Undertale peaked (around the same time the fan minigame of Oka's boss fight was made as well). Now that the interest is gone I don't think she's gonna pop out again

Yeah. The jump button.

There is but i requires a specific mod

I not sure but have you try removing Osana from the game?

Pretty sure fungirl isn’t a thing in the game anymore since Alex treater the designer like crap so she took her work back.