My girlfriend is acting weird

I've been dating my girlfriend for almost two months. SHE told me that she loved me first, etc. Even two days ago she told me, "I love you so much and I wouldn't do anything to hurt you on purpose. Even if I ever did hurt you, I wouldn't let you walk out of my life." She also tells me that she loves me, and even that night she texted me saying, "Don't worry about anything. I love you so much." Because I was worried about how she felt about what happened with her friends. Now, we spend every day together. We're also eachother's firsts.

3 Days ago she said "Oh, I have to go to a dinner with my dad," and left my house early because she had some drama with her two friends who were over and used that as her excuse to leave early. I found out the next morning, as well as her parents, that she spent the night at her other friends house, drank, and smoked hookah. Now, I wouldn't mind if she would have told me the truth. I understand, sometimes you just want time with your friends. But I addressed this to her before she left with her brother, if she ever needs a day off, to tell me.

When I confronted her about it, all she said was via text was "I don't know what to say." Got her phone taken away an hour later, after rejecting 2-3 of my calls and texts. So basically, she's grounded for two weeks, has her phone/internet taken away, and is getting picked up RIGHT after school and being taken to her parents work for 3 hours to do homework. (I've never seen her parents this mad)

Now, I understand that she's going through a lot. But still, I feel awful, she LIED to me for the first time. However, I understand why she's not feeling well. She got caught by both her parents and I. I don't think that she expected to by either. So this morning her dad came and got her school folder, she stayed in the car, he told me "Well, she's going through a lot at the moment so I just got out and got it. We went down pretty hard on her."

Do you think that she feels guilty, or is already going through enough and is afraid of my response?
I honestly do not think that she'd cheat as her brother cheated on her best friend, and her mom practically cheated on her dad. We're also very close and she's honestly very against it.

So I wouldn't get at that, although, some guy that sort of likes her was there. Her dad loves me though, so I'm pretty sure that if there were any marks on her neck, he would've hinted me. She also doesn't have the mindset/conscious to hold anything like that in.

Thanks.