mother-in-law problems/ my own issues?

here is my problem

I have anger problems I suppose...I have conflicts with my family...although to me it seems that it is them...it has to be me because I am the one that has them. How do I control this and not take the bait when they are baiting me? I also have serious issues with conflict resolution...

mother-in-law---my mil is mentally ill and has empty nesters bad, hates me, I feel like she tries to sabotage me and turn everyone against me every chance she gets. She gets in my face all of the time and tells me to hit her etc... (I never have) .She gets the kids pumped to do something and then starts a fight with me and tells me nevermind take the kids and go (so the kids are mad at mommy because they can't do whatever it was). She calls my husband and tells him lies, I think she wants us to get a divorce or something.

Here is the issue, we need her, we only have one vehicle and a busy schedule...she watches our kids on tuesday evenings and wednesday morning/afternoon and my husband borrows her van during this time because they have multiple vehicles...I can get alternate child care but not a vehicle for him...I have to fix this before tuesday so that he can go to a mandatory meeting for work and I can take two final exams (both places are 40 to 70 minutes away from our home so we can't find a ride)

So how do I patch things up with her...I kind of flipped out because she pulled that crap again with the kids and I am sick of her making me out to be the bad guy.