Need advice on being a suspect on vandalizing a car!

Hello. My name is Liana and I'm 17 years old and living in Irvine, California.
So last year I argued with a friend, X(who lives in the same neighborhood as me) about politics and we've never talked since. So his car got vandalized about 5 times this month. Yesterday, a cop showed up at my door asking me about my whereabouts on Friday because X's car got vandalized again. I told him, with my mom present, that I went to school at 7, I came back from school at 3:30 and after that I was with my mom, because she works on Fridays from home and at about 7 I went with her to a ice cream place. He also said that he was asking me questions because X told him I was the only person X ever pissed off. Today another cop showed up asking the same questions, because X's car got vandalized again. I told him I spent the day studying and my mom was once again with me. How should I handle the situation? Should I be accompanied by someone at all times, just in case the cops will bother me again? Can they arrest me or something, just because X said I was the only person he ever pissed off? Should I hire a lawyer? I haven't done it, by the way. I am a straight A student taking 3 A.P. classes. I do not handle things this way.
By the way, I do not know much about U.S. laws, as I came to the U.S. from Europe about 4 years ago. I got my Green Card last year.
Oh, and if the cop shows up again and my mom isn't home, can I tell them that they should come back when my mom will be home? Will that be a bad thing or a good thing?(I am home a lone from 5 am to 6 pm Monday through Thursday).
The only reasons why I am spending so much time with my mom is because I have a lot to study(3 A.P. classes plus the rest of my courses, which I take at the harshest high school in Southern California) plus I am on lock down until I'm done with my SATs.
And plus, I'm not the partying type. I only have two friends.
Please help! I've never had problems with the police!