NEED ADVICE! FAMILY PROBLEMS!

So my SO and I decided we didn't want a baby shower but my mom had already started planing one! Now my SO feels disrespected that she is going on with the shower anyway even tho he said he didn't want one. But also my mom feels as if she has the right to do so because it's her Grandbaby. I understand both sides but now it's cause trouble serious problem in my relationship and stressing me out. ANY ADVICE! Please help.