It wasn't, you're just oversensitive.Except it wasn't done as a joke it was done to make sure no-one missed the fact she was a lesbian to say "Look we have a lesbian character here" to try and look good to a certain audience who will blindly flock to support a character and attack any-one who dares say the character isn't very well written or complex.
And to back that up, you pointed to characters you think bring it up too much.That often in media gay characters are reduced to having being gay be a main core character trait with little other personality.
Except they don't bring it up as much as straight characters do. And you've got no problem there.