Unlinking Fortnite account from Ex GF Xbox

My Ex Gf has my Fortnite account tied up in her Xbox account and I need to some how log her officially out of that account. She has been spending my V-Bucks and logging me out making it basically impossible to play the game since I have spent so much time and money into the game. The account I can get on is all mine except her Xbox name Brianna xD7592. If there was a way to merge both my accounts move them to my other main account on my Xbox profile which is Sourman28 with my name Matthew Cahal in order to kick her off since we once shared the account. If possible I need to speak to someone on the phone to help fix this issue or she will continue to spend my $ on things. I have changed all my passwords and usernames on my PC, but it all seems to run through her Xbox which is locked. I need help bad or I will have to delete everything.

:)