What does it mean when a girl invites a friend?

So, I'm a junior in college and I don't have much experience dating. Recently though, I met this girl that I like and I thought we were hitting it off well. Now I'm not so sure though, here's some background info. I'd appreciate any advice!

So, I actually met her accidentally on Facebook. I messaged her thinking she was someone else lol. Then we started chatting, and she seemed cool, so I asked her to get a coffee on campus. That went well, I thought, we talked for about two hours. She did insist on buying her own coffee, but she's pretty liberal so I don't think that necessarily speaks to whether she viewed that as a date or not.

So last week I said that we would hang out this coming weekend, which she agreed to. It was over text and she texted me very enthusiastically something like "Sure, I'd love to!" But she uses exclamation points a lot, so I don't read too much into that. So I suggested that we go a restaurant she likes and a movie.

She said that was cool, but then she added that her roommate "also would like to come." I'm figuring that's code for "I asked my roommate to come along," so I said that was okay to be polite, but I'm wondering why she would do that. The way I see it, it's one of three reasons:

1/ Worst-case: she doesn't like me romantically, and she wants to make that clear. When we talked before she didn't mention anything about a boyfriend, so I doubt that's the issue.

2/ Middle-case: She has no idea that I meant any of this romantically. In that case, how do I clarify my intentions?

3/ Best case: she's interested but doesn't trust me enough to go off-campus alone with me yet. (I'm 20, and she's 17 and a freshman so maybe it's intimidating to her. She's not really the timid type though.)

If you guys/ladies had to guess, which do scenario do you think it is. And how would you ask when we go out? Should I still try to flirt or show interest even though there's another person there?
What does it mean when a girl invites a friend?
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