Am I overreacting?

I’m new to DnD so I’m not sure if this is just me being petty or if it’s actually annoying. Basically, my gf and her roommate are into DnD, and wanted to start a campaign to get the rest of our group involved. My gf’s roommate kindly offered to DM for us despite being nervous as it’s her first time. She tries everything to make the campaign beginner friendly and fun for us, and I love it so far.

My roommate, after sitting out the first two sessions because they couldn’t come up with a character, finally joined us last week and it was kind of a nightmare. They got pretty intoxicated (even had two drinks in their hand at a time) when everyone else was sober and had asked them to stop drinking. Then it became very clear that they had the most annoying type of character, who either wanted to fight or fuck everyone we saw, despite the fact that we established a clear boundary that sex was a no in our campaign because some people were uncomfortable with it. If they had to do any roleplay or anything that wasn’t battle or flirting, they started to complain about the game being boring and how they needed to be drunk to make it “more fun”. I could tell this hurt our DM’s feelings bc she tries so hard to make sure everyone is having fun.

I don’t know what to do about this and I want to be sure that I’m not the problem here, so any advice helps.