So very many things wrong here.
First of all, except when outing you and silencing you are one and the same (angry mobs will descend and murder you if you’re outed), the 1st amendment doesn’t guarantee jack shit in the way of anonymity.
The first amendment provides rights to freedom of speech, the press, assembly, exercise of religion, and protection from the government establishing an official religion. Unless outing someone anonymous is effectively the same as silencing them, the first amendment provides absolutely no protection whatsoever. There’s nothing in the language that even by the loosest construction would indicate that it doesn.
Second, the first amendment is part of a document regulating our government. Google, surprisingly, is not the government.
When a company is served with a legitimate subpoena, they are legally obligated to comply. Certainly they can give the target of the subpoena the opportunity to challenge it in court or, in extreme cases, challenge it themselves. In this case, in fact, they did do the first of those. But the court upheld the subpoena, so it was Google’s obligation to comply. If it had been unconstitutional, that would have been an issue with the court, not Google.
Third, the subpoena absolutely was legitimate.
This is a pretty clear case of defamation of character. In a case such as this, a subpoena is absolutely legal and absolutely should be served.
In summary, the 1st amendment does not protect anonymity, Google has to comply with court orders, and you ma’am are an idiot.