Family/Tenant Eviction

OK this is going to sound horrid because it's my family member, but we need to sell the house we inherited that she lives in but does not own- she pays $700 to help with bills but this is legally considered rent I believe. She got a lawyer and said she wanted us to treat her as a tenant and not a family member as shes technically an at will tenant. (there's a lot of bad history there and she's a textbook narcissist)

She signed an Agreement to End a Tenancy but is now backing out of it. In the agreement we offered to give her $20k to help with her move so long as she moved out for March 1st. She has now made it clear she has no intention of leaving.

I'm looking for advice on if my plan is correct.

I plan to file the agreement with the LTB along with an affidavit stating the agreement is true and was not a condition of her renting as required by the LTB. I then plan on filing a notice to evict on the agreed upon date. I do believe she will fight it and the LTB may give her an extension which I'm fine with. I just want to have an end date to this nightmare. Is there anything I'm missing that might bite me?