Baby Shower

My In-laws are insisting that I have a baby shower for the new baby next month. She was born in July, so she will be 6 months old then. We didn't have a shower before because 1) I was finishing up summer classes. 2) The house was a renovation disaster and they insist it needs to be at my house. 3) My soon to be ex husband hadn't had a day off in 90 days. 4) She is my 3rd child and I bought her everyhing she needed. Now they think after Christmas will be a good time for the shower. They have NOT bought the baby a single gift because it seems that they want to have the big show of giving her something with everyone around and the whole thing just seems effed up to me. If they are going to do this anyways, do I need to even show up to this disaster?