My first property (CA) closed, Seller says she's not leaving

[James Thomas]

Hello, I met someone yesterday who recommended I post on these forums to get some valuable feedback from this community - many thanks in advance. Going to condense the story as much as possible so it's not horribly TL;DR. 

I just purchased my first property in Southern California and got a great deal. My family is somewhat involved in real estate and an old client of a family member was foreclosing on her home (she was in a private money loan). She owed around $250k, the house is worth around 600k but comps are around 700k+ after rehab. I don't have a ton of money, but I offered to pay off her loan and give her around $100k to walk away, which is the max I could afford having to put a 20% down payment on a fix & flip loan, she agreed. Escrow closed at the beginning of the month but since the seller didn't have any money she asked that she be given some extra time to find somewhere to move. I agreed to give her until June 1 but held back $20,000 in escrow that would not be given to her until she permanently vacates the property.  Also, after 7 days of closing, I am deducting $150 per day as long as she stays in the house (all signed when closing). 

It's been several weeks now and the woman has snapped. She says that she never agreed to sell her house and that she's not leaving, which is insane. She is trying to claim that she never went into the escrow office and signed anything to officially sell her house (she did, I have the deed). I'm a little shocked by all of this but now I am just trying to figure out what I should do to move forward. Do I have to evict her? She's not a tenant at all - she's a seller. I also have a very short loan period because it is a fix and flip. A friend recommended that I go on redfin and opendoor and see what kind of offers I could get for the house as is (it needs a lot of work but is in a prime area). The offers are around 600k. Should I just take a cash offer and walk away? Or should I rough it out and possibly get something like 700K+ after rehab?  My fix and flip loan has a 40k rehab budget built into it. Thanks in advance.