Gf won't stick up for me with her friends

So, I'm (30M) in a serious relationship with a woman (32F), and 95% of the time things are great! But the other 5% has got me worried...

She has a friend thats about the same age & gender, and when they're together they often like to commiserate on the many problems they've had w men, specifically in past relationships and in general everyday life (work/college/passer-by's etc...)

Sometimes this friend can get a little too specific and make comments and digs at my expense. Most of the time these are harmless and I can tell its a joke, but sometimes I feel like she's being disrespectful and crossing a line by saying things I and my gf know that I feel is...well, kinda like bullying. And my gf laughs along or piles on top.

Ive spoken to my partner about this, and she tells me im being sensitive and that I shouldn't let it bug me. Ive countered that as her partner I would appreciate that she say something about how as her partner I should be treated w a basic level of respect and decency.

If I get upset about something she says I don't make a scene or get nasty, but I do expect my partner to say something along the lines of "hey that wasn't okay" or even "please dont disrespect my bf with those kinds of comments"

My gf does not have a lot of friends, and I worry that she's more concerned with holding onto a friendship than she is with holding said friend to a certain standard and making sure they are decent to me.

My rambling comes down to: is there a way for you to ask your partner about holding their friends to a certain standard, without telling them what to do or what to say to a friend?