I [30M] caught my girlfriend [26M] acting arrogant/rude to other women because of my job. I've talked to her but she won't admit it. What can I do?

Keeping this short. I've been dating my gf for 8mths, so I know it hasn't been long. She works as an English teacher and I work in high finance at a big bank. We live in Asia, so apologies for any awkward English. I work long hours but she's been very understanding and supportive and exactly what I'd want in a partner.
Anyways, last weekend we had a roof party at my place and tons of people attended, lots I didn't actually know (friends of friends). I was walking around talking to folks, making sure everyone was having a good time, when I overheard my gf talking to a group of women. My back was to this group while I talked to another friend so I basically heard everything beginning to end.
It started with a woman asking my gf what my work-life balance was. My gf said not great but that's what you gotta do for the money. Then this woman said that she was looking for a career in finance too so she might talk to me later to get some advice. My gf kind of chuckled then asked her what she's currently doing/where she went to school/etc. After hearing the replies, my gf openly laughed in a cruel, mocking way and told this woman that she'd have a better chance just sleeping with a director and getting her in that way, because her credentials were "nothing to write home about and I know important people when I see them." She said "don't bother asking my boyfriend, you'd be wasting his time too... sorry!" The woman didn't say anything, but the other women in the group kind of awkwardly chuckled. For the record, I've never heard her talk like this. I was so surprised. I slid my way through the groups of people to separate myself from her but it made me feel uncomfortable to hear her talk like that. Her attitude was so arrogant, and furthermore it completely misrepresented what ACTUAL advice I'd give to that woman.
After that I asked my girlfriend why she was being so rude to that random woman, that I would never tell someone they had no chance in any industry. She acted innocent and kept maintaining that I misheard things because the party was loud and it might not have been her talking at all. I am like 99% certain I recognized her voice and speaking tone and also the fact she said "my boyfriend, [my name]" (there is only one person there with my name), but obviously I can't prove it. What to make of all of this? Thanks.

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tldr Caught my gf being very arrogant/rude to party guests while she thought I wasn't there. Confronted her about it but she claims it wasn't her completely. I'm pretty certain it was, but obviously I have no proof. What to make of this?


Source.

These threads always have the "tldr" (too long, didn't read) synopsis at the bottom. Why not just go for that on the first place

Sounds like your gf is on a high horse and thinks you are better then everyone else.