Baby shower drama

The moment we told my SO's family we were pregnant his sisters asked if they could throw a baby shower for us. Being grateful and appreciative we of course said yes. I also had my friends ask if they could host one for us. Considering we have a large amount of friends that want to attend and family we decided we could have a friend baby shower and a family one. The friends shower planning has gone amazing and they have worked together without any issues. The sister one on the other hand..... That's a different story. So when they asked to host a shower I politely mentioned that my moms best friend (who is basically my 2nd mom since mine passed away 6 yrs ago) would love to help. A month ago I reminded them and gave them her info. Which they responded "thank you! Great!". My SO asked the youngest sister (who has a history of outburst) if my moms BF had been included because it is really important to me. She exploded. Saying "we did include her, she is invited. And we don't want her help" then she went on to complain how much it is costing them and how inconvinenient it is for them. Then my SO and her got in a big fight because he got defensive since #1 we didn't ask to have the baby shower and are simple people and #2 she was so rude when we were TRYING to give them help. Sooo my question is. Should we cancel the baby shower since it seems to be such drama or keep it on because his sister and Mom are not of her opinion and it's all because the 1 sister is a diva and things fell apart in the first place. Thank you!