Thank you for using our forum. My name is ***** ***** I hope to assist you today.
I am sorry to learn about this situation.
If the home is still within the will or trust (so the second sale is still benefiting that entity), this may be a good time to retain what is called a "probate attorney" (the amount in question is certainly sufficient to warrant doing so, and having your mother sign documents while in the nursing home is a hallmark sign of what we refer to as "undue influence" (a form of financial elder abuse and making the document in question invalid)) - but it takes a good attorney to help you do this, you can try doing it yourself, but again, with the amount in question it is worth retaining counsel.
Even if the home is no longer controlled by the trust/will, it may be possible to contest the probate matter simply based on pursuing the individuals for money damages (this just makes it a little harder to collect (but not impossible).
I would at least encourage you to visit with a local attorney and go over the details of your case.
Fortunately the majority of these attorneys will provide you with a free consultation, and many will represent you on a contingency basis (they will advance the costs of litigation and legal services in exchange for a portion of your successful settlement or judgment). You can find local attorneys using the State and Local Bar Association directories, or private directories such as www.AVVO.com; www.FindLaw.com; or www.Martindale.com (I personally find www.AVVO.com to be the most user friendly).