Quit claim deeds are not hard for an attorney to prepare, so as long as you went through an attorney it may be quite difficult to find something wrong with the deed. My colleague mentioned some of the grounds by which the transfer could otherwise be challenged. Once a gift of property has been properly transferred and no surrounding circumstances allow the gift to be challenged, your grandmother is not going to be able to get it back.
If there is no claim of fraud, duress, etc., the quit claim deed vested title in you and your partner. Did you get title insurance? If so, contact your title insurer immediately.
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