Should I throw a shower instead of MIL?

CowgirlK39

My SIL is expecting her first child this fall. She really wants a shower but cannot afford to do it herself. My MIL said she would do it, which is the worst idea ever. Some backstory: my MIL is a self centered woman who finds every opportunity to make everything about her. My mom was going to throw us a bridal shower last summer but my MIL insisted she throw one as well so we had two. The one MIL threw had people who were not invited to my wedding because she "wanted HER friends there." I was so embarrassed but MIL paraded around like she was the greatest event coordinator ever.

She is doing the same thing to SIL now, demanding that these random friends of hers be allowed at the shower. SIL does not want to seem gift grabby and certainly does not want people she does not know to be at her shower. We both understand the fact that MIL has a say if she is paying, but we have seen what happens when she throws showers. I cannot convey just how BSC she is. 

I feel bad so I said that I would try to get SILs friends to join with me and help throw the shower, just to take part of it out of MILs crazy hands. But I do not want to make MIL mad. How can we help stop the tension between MIL and SIL without seeming like we are completely taking over?