Guest List- Inviting Cousins issue

When my FH and I made our guest list we picked those we care about and have a list of 110 people (about 50/50 for Bride vs. Groom). We selected a venue that we fell in love with even though it was a little out of budget. Initially the MOG was fine with my FH not inviting his cousins as they are not very close and some haven't even spoken in over 7 years. Last night she found out I am inviting my cousins who I am very close to (I went to grade school and college with one, another I text on a daily basis, last weekend I went to one's wedding etc.) She says that "it's not right" that we're inviting my cousins and not his. He suggested we only inviting the ones he sees at least once a year and she said we can't pick and choose. This will add 20 people to our guest list. My fiance really doesn't care if his cousins come and would prefer his friends (who are like family) were at the wedding instead. His cousins normally aren't even invited to family parties. Are we in the wrong?