She can't prove it, and such a serious allegation needs to be proven.
In the court of public opinion? No it doesn't. Sorry. I believe it, because it is easy to believe. And it is far from the worst thing about the mentally ill president.
The court of public opinion isn't going to matter when Trump sues her in civil court for libel.
She wasn't even born when Trump took the SAT's, and the SAT's aren't normally a topic of mundane conversation 17 or 18 years later, when she would have an appreciation for what they are.
Only a complete fucking idiot would believe such a thing...