My [19M] college roommate [18M] is getting married to his girlfriend of 3 months. I think it's a terrible idea, and he overheard my girlfriend [18F] talking negatively about it.

My roommate and I are sophomores in college and share an off-campus apartment.
My roommate has very limited dating experience, but at his summer job (approximately 3 months ago), he met his current girlfriend. I've only seen her a couple times, and tried making conversation but she didn't respond well (she's Brazilian, English is her second language), and it seemed like they wanted to be left alone. Since I don't know anything about her or their relationship, I don't have an opinion on either of them.
I do know, however, that my roommate's parents are strict Koreans, and he's currently hiding the relationship from his father (who would strongly disapprove of an interracial relationship), while his mother knows and only mildly disapproves.
The past weekend I was away and we had the following text exchange:
The next night, my girlfriend was staying over and while she was in the shower, I had the following conversation with him:
At this point I had *plenty* of other questions to ask, but it was past midnight and wanted to jump into the shower, so I left it.
I jumped into the shower and told my girlfriend that it was legitimate, and he was really getting engaged. I know I was probably wrong to tell her, but
a) she already knew about it, since she knew about the initial text message (which didn't mention anything being secret), and
b) she hasn't (and will never) see or meet his parents, so there isn't a risk of word spreading to them (assuming that's the main reason why it's a secret).
While in the shower, she was going off about how illogical and ridiculous the whole engagement was. She was making harsh, but accurate statements that I mostly agreed with. She mentioned how he's a sophomore in a rigorous major (MechE) who plans on going to graduate school, how his parents will essentially disown him if they're truly strict Asians, and especially how he's 18 and they've known each other for three months.
I agreed with all of her points, but tried to keep quiet in case he overheard. And sure enough, when I left the bathroom, he called me into his room and was furious (yes, he spoke to me and not her). He didn't seem necessarily upset that I told her, but was more upset that he could hear her trash-talking the engagement "ten feet from his bed", in his "own house" which he "pays for equally". In my opinion it seems like he was probably eavesdropping, in which case is destined for hurt feelings and hearing things you weren't supposed to. If I locked my friends in a room at the beginning of my relationship and pressed my ear to the door, I'm sure I'd hear some negative things too.
I agree with all of her points. "Love" (or whatever that means at 3 months) isn't enough. In three months, they've probably never fought, never made-up, haven't lived together, or even know each other's living habits. Not to mention the other glaringly obvious problems with getting married so young (while still in undergrad) and so soon.
Plus, ever since I’ve known my roommate (1 year), he’s always been pretty rude towards my girlfriend, which I think exaggerated why she had an animated reaction.
It's not my relationship and for the most part I don't care. However, now there's a problem and I'm wondering how it should be addressed. My roommate is pretty closed off and holds a huge grudge, so imo an apology won't make a difference and it's best to just drop it, but she says it would be for her own benefit more than his. And it probably wouldn't hurt, at least.
TL;DR: Roommate making a pretty irrational and terrible life decision, normally not my problem but he eavesdropped on me/my gf being a ****. What do I do?
Thoughts? Thanks a ton


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