A: The account here is a little hard to follow. It is highly unlikely the social security administration would recognize this arrangement as a common law marriage entitling your friend to social security benefits. A common law marriage under Texas law is not created just because someone declares it - rather, the focus is on whether the couple held themselves out to the community as being married. Does not sound like your friend has even a slim chance of convincing SSA she and the old man were "common law married".
I don't think your friend will be exposed to a fraud charge if she presents the document to SSA - although it is going to look very suspicious: younger caregiver presenting a document drafted by a dying old that would allow her to get his social security. SSA could contact other authorities to investigate whether there had been some type of elder abuse. I could see why. In fact, I am very suspicious of your friend - at the least she sounds very unethical. May I ask politely why you are friends with a person who moves from the grandson to the old man after his spouse dies and may have convinced the old man on his death bed to give her his property?