Hi there OP. I think in your case, I would give yourself at least 3 months before you make any big decisions with your horse. It takes at least 3 months for you and your horse to start to bond. It can be difficult to know whether any particular horse is a keeper until you have this time under your belt.
I remember when I first got my 1* schoolmaster on loan. When I first went to see him in the paddock, he wouldn't even let me walk up and pat him, as he didn't know who I was! After about 3 months, I distinctly remember bringing him up from his paddock to ride one weekend. I had just tied him up and was chatting to a friend. He turned his head to look at me and the look said "Oh, so you're my person now!" I turned to him and said "Hello Sweetheart!" 
From there the bond grew and grew. Yes, there were times I just wanted to smack his little red hiney, but I would always remind myself that a bad day with my horse was better than a good day with a lot of people
. I ended up loaning him for 5 years and in the end, he trusted me implicitly, and I would have trusted him with my life.
He was quite a nervous TB as he was low man on the totem pole, so was always on the look out for danger. One time, I was riding alone, under lights in the arena, and the cow and the dog next door were playing stupid chasey games while I was schooling. We had just started our canter work, and the chasey games started. I could tell from some very subtle signs that something was upsetting him, and our 'agreement' was that if something was upsetting him, he was allowed to stop and look at it once, but then it was back to business. So I stopped him just as the cow chased the dog down the fenceline, about 30m away from where we were. And all horsie did was stop and look at them
, although I could feel his heart beating like a pounding drum next to my left boot. We stood there for a minute or so, while I praised and patted him for being such a good boy
.
And good horses are hard to find. If the previous owner is looking for a horse, it will probably take her much more than 3 months to find something that she likes. I would just use this time to get to know you horse and figure out her personality more, and whether it meshes with yours. Then you can decide whether she is a keeper, or whether you would rather work out something that suits your situation better.
Hope this helps.