No it isn't. Statements like this put people off doing something as normal as what OP has done because they're shamed for doing it.
What exactly is the opposite or what should she do instead to not be seen a "try hard" or "right on" - not buy a doll of any other colour or race? In other words, maintain the status quo? Or perhaps not come on mumsnet to ask a question, like other posters do? Or is it only "try hard" because it has to do with race or Black people?