I (25M) am at odds with my GF (26F) due to her colleague's (28F) new boyfriend (30M). How can we come back from this if she keeps bringing it up?

Apologies if I rant for too long, my mind is pretty jumbled right now.

I've (25M) known my girlfriend Aubrey (26F) for around 6 months now, and one point of what used to be minor conflict was her friendship with her colleague Paula (28F). To be frank, I think Paula is a bad person based on the things Aubrey tells me about her, which is a whole list of crappy things.

Paula has been dating on apps for as long as I've known Aubrey, and she would say that she's on them because she wants to find a life partner so that her elderly parents could feel assured that she is not alone if something bad happens to them. But then she would specifically match with foreign rich men only, even when it's so clear that they are not looking for anything serious. She would sleep around if it meant getting monetary gifts like expensive handbags or getting to stay at expensive hotels. Paula indulged in these sort of things no problem, even bragging about it to Aubrey consistently.

I started questioning Aubrey's friendship with Paula when she mentioned that although Paula matched with guys who were genuinely interested in a serious relationship with her, she had no interest in them because they weren't wealthy. There was a guy she was leading on for a few months because she knew how much he liked her, so she used him as company whilst she was sleeping around without his knowledge. I already think that's pretty gross, but she even planned on trying to get some money out of him despite already knowing that he isn't wealthy.

At the time, I talked to Aubrey about this and wondered why she was friends with someone like this considering how different she is, and she said that she doesn't actually have many friends and is pretty lonely, so Paula is one of the few friends that she has. And that she does criticise Paula for her actions, and actively discouraged her from trying to get money from the guy she was using. She also added that this was Paula's own life, so it wasn't really anything to do with her anyway, and so nothing to lose sleep over. I accepted it as some sort of culture clash at the time (I work abroad) and didn't really say anything else.

Recently though, Paula has a new "serious" boyfriend Jim that just sounds suspicious as a whole. Despite having never met in real life, they were already planning marriage and having children. He's from another country so the most they've done is video chat, but Jim has booked tickets to fly here in a few days to finally meet Paula. Before his flight had even been arranged, they were also already talking about Jim moving here, despite Jim apparently studying very hard internationally to be living in the country that he is now. They discussed him getting a job and a work visa here too, finding an opening at the company I work at. This seemed fishy to me too, since he apparently has a well paid marketing job, yet he was willing to throw it away for a pretty underpaid job with a lot of hours. This is a whole other situation, but long story short, I refused to help Jim at all with this, much to the disappointment of Aubrey.

Aubrey feels that this is Paula's chance to finally be happy after meeting so many unserious guys, ignoring the fact that Paula was living it up at the time with the same unserious guys. When I brought up how quick their relationship was going, Aubrey responded that Paula has been waiting for a guy like this and she would obviously jump at the opportunity, and then she also defended Jim, saying that he was a decent guy (despite Aubrey having never met him). Aubrey also mentioned again that it did not directly affect us, and that I'm way too invested in this situation.

But if Paula is really such a good friend, surely you would say something to her about this? To not even have concern regarding how fast things are going nor about the safety of her friend seemed so disconnected. In the grand scheme of things, I did see that perhaps this was getting to me too much, so I let it go as Aubrey said herself, Paula was a grown adult who could make her own decisions.

However, Aubrey is not letting it go after I refused to even entertain the idea of me helping Jim with getting a job. In her perspective, I am actively causing an issue and potentially damaging her friendship with Paula. It's all she talks about now and I'm getting tired of it. We had no major issues in our relationship before all of this and it just seems so bizarre since the point of conflict isn't even directly about us.

How can I communicate with her so that she will just let it go? How can I get her to understand where my point of concern is coming from if she's just focused on the happiness of her friend?

Tl;dr: My girlfriend's colleague who has a bad track record seems to be getting into a suspicious relationship, and it's been causing trouble between us.