Limited spots for our wedding

My fiancé and I are getting married soon. We only invited like 20 people and I friend I was close with we had invited prior to sending invites out. We had a falling out but I decided to still invite her since we’ve been friends… her on again off again relationship guy is a dick…. Not fond of him.

Originally she had told me he won’t come to the wedding… so when I sent invite I only sent it for her…. Well I messaged her asking if she’ll be making it and she said yes and a plus one…. Well…. He wasn’t invited and we only paid to have a very small intimate wedding….

I messaged her saying she originally told me he didn’t want to come…. She said well things have changed…

I’m in a pickle and don’t know what to do,

We don’t have family helping us pay for the wedding and we’re only allowed a certain amount of chairs….