Do I let my ex bring her new BF to my party?

Basically, I'm having my 18th this weekend and im having a party, my ex asked me whether she could bring her new BF. We broke up a year ago and I don't believe I hold any bitterness towards her or him, but I just wouldn't feel right letting him come. I'm a nice enough person, but would you let him come if you were in my situation?