You need to press charges against your brother, if that is what you are asking.
That's a real mess. Upfront: I'm not a lawyer, so I can't offer legal advice. And you definitely need a lawyer. However . . .
First, you're in deep trouble, and you keep compounding it. Let's start at the end. You can not do a lease-option (or purchase option) in Texas for more than 6 months unless you're very, very careful. See the source listing below. But the point is: You didn't do what's required. (In the other 49 states, you'd probably be OK. Not Texas.)
Second--though some lenders don't care--a lease-option is the conveyance of equitable interest . . . just as if you'd sold it to your brother. You've conveyed an equitable interest to your tenant. Your lender didn't like it before when it invoked the "due on sale" clause. It probably won't like it this time, either, if it finds out.
Third, it's admirable that you want to do the right thing for your tenant. Still, you have to protect your interests, too. And your tenant should have taken certain steps, such as a title search, to make sure that your brother really owned the property. So she's got some responsibility, too.
OK. So what do you do? Short answer: See a lawyer. I suspect that what needs to be done is getting rid of the purchase option. That may not be too difficult since I'm sure it wasn't properly drawn up, and probably doesn't comply with a bunch of Texas laws. But that's hanging over your head like a sword. Then, convert the tenant to a true tenant. A pure renter. Or else sell her the property. If she can get a loan, great. If not, you could do owner financing though, for a number of reasons, I wouldn't recommend it in this case.
Meanwhile, make sure that everything your brother mucked up has been straightened out and that you're clearly and solely on the deed. You'll have to make sure everything's OK there (no cloud on the title) before you even consider selling the place.
But, again: See a lawyer. Make sure that the past problems with the deed are corrected. Get rid of that purchase option agreement. Decide whether the tenant will remain as a tenant. Or sell--cleanly--to the tenant.
That's what you do.
Hope that helps.