Double Sale of same house...Need advice!!

[John Bourque]

So I live in a suburb of Boston Ma. I put in an offer to purchase this SF house as an investment property. On market for $499...Seller's realtor claimed there was another offer so I went above ask to $515k. Offer accepted and signed by both parties...It comes to light that the seller is really the realtor who did not disclose this. Fast forward to P/S which is today. She now sends a text to my realtor and states that she is backing out of the offer from me because she had a higher offer after our signed offer. If we would like to match said offer, she will proceed. We reached out to her broker and informed him of this situation. So we proceed with signing the P/S per the offer.  My attorney lets her know that what she is doing is against the law and breach of contract. Her response is she will just take the house off the market ???? Is this real....has anyone encountered such a thing...what is my recourse?