I like this girl, and I think she USE to like me, but now she ignores me alot.?

idk what happen. did i take too long to ask her out? we really never hung out much. i only see her on the bus and thats not a good place to talk because so many people are around. when we first met she liked me a lot. now its just going downhill. she ignores my texts, my IMs. i dont know what's going on. i'm gonna ask if she wants to hang out later but idk..my friends tell me to tell her how i feel but usually people do that when they are really close, and we aren't as close. i've only went bowling with her. what should i do? i really like her. i wanna spend time with her more so we can get closer. right now we are having our christmas break, and i think it's the perfect time to hang out. should i tell her how i feel? how and when should i tell her? should i wait?