This becomes a race notice issue. See HERE and HERE.
NY is a race notice state. This means that one who pays fair value, does not have notice of any other earlier conflicting interests, and records first, wins and will have priority over any later recordings.
As such, technically, since she never recorded it, one can sell it and the buyer would record it and be in superior possession.
However - and this is me being thorough - she may attempt (however unlikely) to try to attach interest to the property claiming that $3,000 was owned and that the buyer knew of this fact (how she'd prove this, I do not know). If she does this, she is likely to fail (because NY is a race notice state), but the buyer can possibly sue you for fraud or seek indemnification in fighting her claim. Chances of this happening are VERY SLIM, but I am being thorough here and am simply wanting to be sure you get every angle of this situation.
If someone in your situation wants 100% guarantee that she won't complicate matters, then I would pay the claimed $3,000 be it a real claim or not, and then get her to sign a QUITCLAIM DEED to you, formally giving away any possible interest in writing.
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