Can my school suspend me for this? What are my rights?

Me and this girl have had problems because im friends with someone she hates. This girl is in 8th grade and im in 10th grade. I was talking to her on facebook and she started swearing and being a b**** so I swore back at her. Well her mom is crazy and hacked into her daughters facebook. Printed of the convo and gave it to our principal. Me andmy friend got suspended and nothing happened to the 8th grader. I understand that I swore alot but it was outside of school. It was on my personal facebook page. And I did NOT impose ANY threats. I feel I got punished unfairly and that she should at least get some sort of punish for everything she did. Like purposly pushing kelsey in the hallways and stuff. What are mine and Kelseys rights and can you give me a website that would explain our rights, we live in michigan. I don't think the school should be able to punish me for a convo that happened outside of school. Mine and Kelseys parents are very mad and they're going to be a huge meeting tomorrow. I would just like to know our rights so I can go in there maturely and know what I'm talking about. Thank you for your help!