Question about getting a villager to leave

Halp me please! I have been trying to get a villager in boxes for literally 2 weeks (TTing back and fourth 3 days at a time, talking to everyone, having only flowers in my pockets, swimming into the ocean for 6 mins to get them to ping...you name it) and SHE.WON'T.LEAVE! Everyone one else has asked to leave 1 or 2 times now, I fulfill all her requests, talk to her until she asks to be left alone. Idk what to do anymore! She's just so dang stubborn. What am I missing?!