Friend might be pregnant

So my friend got high with a guy in mid-November, and they both kind of remember certain parts of sex, ad a condom was missing from his wallet.  They don't really like each other like that though, so they've been pretending it never happened, but she missed her period about a week after they think they had sex and she it has been almost an entire month since then and if she doesn't get this period by January 5th we're going to go out and buy a pregnancy test for her. She hasn't brought any of this up to anyone but me, including the guy, and we're kind of freaking out. We also looked up some symptoms of pregnancy, and she had already been having those, but we're not sure because she's still really young (14) and sometimes when you start gettin periods they're irregular, so what do you think?