After I was out with my mates one night and my girlfriend was out with her friends, I went back to my mates and spoke to my girlfriend on the phone to say goodnight and that I was staying at his. After that I poked my girlfriend off my mates account and went to bed, in the morning she poked him back, after that I rang her to ask why she did that and said it was accident when she was closing her alarm on her phone. Could she be telling me the truth? Did she do it knowing it was me? Or was it another reason?
She poked him back on purpose. No biggie. But she lied to you. It wasn't a mistake. And enough with that alarm bullshit. She's lying. End of story. Big biggie. Can you trust someone after they lie to you? No. Not now, not ever.
If I were you, I would seriously consider on breaking up or confronting her with her bullshit. Maybe she's scared of making you mad, but that gives her NO good reason to lie.