Are you even in the market for a new house? If not, let it go and never share with her again.
If you are and you really want the house, get your ducks in a row and snatch it. How can she even afford it? I would also have a talk with her about how this makes you feel - like you aren't friends and she's just using you.
And totally unrelated to the house, stop doing this woman favors. Tell her because of the price of gasoline, she needs to contribute to your expenses or you can't run her or her child around. Just because it's on your way to anywhere doesn't mean it isn't an inconvenience for you.