Advice Needed... How Do I Move On After An Epic Fight?

My SIL and I had an epic fight.  It stemmed from her boyfriend withholding our wedding photos from us (previous story).  She informed my new husband that she as no intention of speaking or interacting with me ever again because I have "hurt someone that she loves for the last time."  She told my husband that he should leave me.  [My husband and I had an on/off relationship during our early years, and I upset her boyfriend over the wedding photos.]  I went to her [and her parents'] house with roses to mend the fences for my husband's sake.  She didn't want to see me; I waited for hours for her and was infuriated.  I threw the roses at her torso, and she attempted to beat me up.  We ended up having a shouting match in the house before it was all over.  It was pretty terrible.  

I certainly did a few things to escalate the fight in my anger.  I am not blameless.  

It has been three weeks since the fight, and I have not spoken with any of my in-laws yet.  My husband says my in-laws are not upset with me; they understand that I'm having a tough time since being laid off.  My MIL said that she is stressed out about other things right now, and will talk to me next week.  My SIL still hates me.  My husband doesn't want me near his sister or at his parents' house when his sister might  be home.  

Any ideas for moving forward?  Anyone have experience about smoothing things over after a fight of epic proportions?do 

Also, his cousin is having her baby shower this weekend.  I was invited, and it is my first invitation to an extended family event as a newlywed.  I already said that I would attend, but I wonder if I should send a gift and stay home.  My husband says to stay home...  but I don't want to let his sister and her anger dictate what I do.  Also, I was looking forward to going!  What should I do?