Sorry, but I read and REREAD the two posts made by Rusty and no where did she/he say anything about something wrong with the horse besides some training problems. Where do the "vet bills" come in or did I miss something. As stated before, she is NOT in foal anymore.
OP, just take it slow. Put her in a small pen, not to small, with the run-in shed, food, and water. Just spend some time with her in her pen, get her used to you and know that you aren't going to ship her off to the slaughterhouse. Once she trusts you, I'd go back and do basic groundwork. Haltering, leading, grooming, picking up her hooves, saddling. Do desensitation work, and A LOT, before riding her, unless you feel comfortable enough.
If you don't have a ton of experience with this, get someone experienced to come help you out, mentor you, etc.
As for being alone, it really depends on the horse. Some can be content with living alone, and others need a companion. You could get a goat, miniature pony, donkey, etc.
Hope all goes well with this horse. I probably would have done the same!