I've done things I shouldn't have, what now?

(Very long post) This is going to make sound like a b**tch, but I honestly never knew what I was doing and I feel bad now.

Well last week I invited all of my friends to pizza hut after the last day of school was over. They all agreed, except for one. She refused because she went there with her family recently and they tried to pay for something with a 10$ gift card, but the employee wouldn't accept it and her mom and her got into a fight with the employees. Since the same people work there every day she never wanted to go. I never wanted to go without her since we were all going and she always misses out on experiences like these.

So this time I tried being forceful, which I now seriously regret. During the last period all of the students were horsing around since the teacher said she wasn't assigning any work, but us two were just sitting in the middle of class doing nothing. So I took my friends backpack.

She asked for it back, but I ran away from her and said that she could have it back after break. She kept begging and asking for it, but I kept it away from her anyway. I told her that she could have it back the next day after school when we went to pizza hut. She said there was no way she going and doesn't see why it was so important to go. I still kept the bag with me. I was going to give it back to her after the school bell rang (which would be in about 20 minutes) and I was able to hold it back from her until then. During that time she was still asking for it back, but while she was doing this she was smiling, and looked perfectly fine. Class was dismissed and I still kept her bag with me.

I went to my locker and I did a good job of making her think that I was seriously going to keep the bag (even though I wasn't) She was asking me stop (still smiling) and I never gave her bag back. Suddenly one of her friends walked by and she was like "-insert name here- help me get my bag back. I tried to explain why I was keeping the bag but she said "That's stealing." and she pushed me against the locker really hard and forced the bag off my back.

My friend was thanked -insert name here- and before she did anything I said "**** you -insert friends name.- don't talk to me" I laughed (to show I wasn't serious), and then she walked away.

People say stuff like "I hate you" and "B*t*h" and things along that all the time without meaning it. So today when I sent her a text asking her to hang out with me at the mall I was shocked when she said

"Who is this." I replied and said "It's -insert my name here-" You deleted my number? That's harsh nvm.

Her: WHY WOULD I WANT TO HANG WITH YOU AFTER WHAT YOU DID TO ME! YOU WERE THE ONE WHO SAID YOU NEVER WANTED TO TALK TO ME IN THE FIRST PLACE! IT'S CHRISTMAS AND I WAS SO HAPPY JUST LEAVE ME ALONE IM SO SICK OF YOUR S***"

I was quite alarmed and said "I was joking! I realize what I did was wrong, and I'm sorry, if you don't want to be friends I wont force you"

She responded with " WHAT KIND OF JOKE IS THAT! YOU HUMILIATED ME IN FRONT OF THE WHOLE CLASS! LET ME TELL U SOMETHING...AT SCHOOL DONT SIT BESIDE ME, DONT TALK TO ME, DON'T EVEN BOTHER LOOKING AT ME, U DON'T DESERVE TO HAV FRIENDS FOR ALL THE JOKES YOU PLAY." (Note:I'm sarcastic all the time, and she hadn't show any sort of annoyance with me until now.)

I responded with "okay", and that was that.

I'd like to say that nobody in the class was paying attention to what we were doing because neither of us are very social people.

Looking back I feel like an idiot, I should have respected her and just excluded her from hanging out after school like I normally did. I'm not depressed or anything, but we are currently working on a group school. It'll be impossible for me not to communicate with her because we have to do the steps together (It's a wood-shop project) Should I apologize again or not? I honestly had no idea she was this upset because she always laughed at my jokes and smiled and went along with everything. I'm not sure what to do. We also have all the same mutual friends so I'm not sure how the situation will play out, as I am typing this she could be setting everyone in our group against me. Any advice is helpful.