I've noticed this trend too - so much so that I started a thread about it the other week. The triggering of women when they see men who date younger women is increasing exponentially. It's become practically the #1 way in which women attempt to shame men these days.
As for her, ignore her. Ignore the replies. I wouldn't leave the group chat though - don't let her push you out like that. Since she is sharing personal things about you, feel free to mention anything she told you about herself that is personal - though the moral high-road wouldn't be to do that - it would be to just ignore her and block her and move on with your life. Feel no shame because you did nothing wrong. Most women, despite liking her post, will secretly be turned on by you.... "who's this guy who can get young girls like that? What's he have that they want? I'm curious about this guy....." Really, she did you a favor. There is nothing to be worried about. If any girl tries to give you sh*t about it, just understand that they are only doing it from a place of deep personal insecurity and they are projecting it onto you, then just ignore it. You can debate them and destroy their arguments with facts but that won't change their opinion because their opinion is solely based on emotion and deep insecurity. Feel sorry for them - their insecurity is likely to play out their whole lives, every day, and cause them a lot of relationship issues over the years.