Hi Greg,
If this were me, providing the money to pay the back taxes was in a bank account or could be borrowed (credit card tax payment, family loan, etc...) I would draw up a (state legal) purchase and sale offer based on "Comps".
Show her the comps you used when you give her the offer, and put a long drop dead date on offer, such as 6 weeks. (she may shop the offer and call a realtor (which means she will lose the commission amount), or she may think on it for a while.
Either way, like in baseball, that makes you the pitcher vs the catcher, and gives you more control over the situation.
If the county forecloses due to taxes you will probably be out of a home, so "Tick Tock" the clock seems to be already running.
An (OWC) owner will carry seems like a quick inexpensive way to buy, although if she has a mortgage it WILL have a due on sale clause and if it's FHA I have heard from others they tend call the due, so think about that.
Also, if it were my offer I'd put a cash kicker in to get her to say yes. Maybe $5,000, just because it seems like this might be enough to sway her to do deal to solve some of her cash flow problems.
Right now there does not seem to be enough of a Stick to get her to sell, so maybe try the Carrot of $5,000.
Maybe set the interest rate just a notch above the current interest rate for an FHA Loan.
Also she may have borrowed heavily against any equity in the home encumbering it with more debt than its currently worth, so look at that too.
Good Luck!