Wedding party

She can be a Bridesmaid (you don’t need another Groomsman), Greeter, Gurstbook Attendant, Hostess, or Reader. Congratulations and 🍀‼️

Your sides dont have to be even, so you could have 4 bridesmaids.
Or she could do a reading?

I agree, sides don't have to be even. We're having 3 BM and 2 GM

A few suggestions

Don't worry about even numbers. Have wedding party walk down aisle one at a time. Your side, his, yours, his... so the singular person doesnt seem unbalanced.

Ask her to be the MC (master of ceremony). Coordinating all the order of events, making some toasts, announcing to guests "the first dance," "time to cut the cake," "garter toss..." that way she has an active roll

Is there a mutual friend that you share that would be down to stand up on his side ? Mutual friends are just as special as his own set of friends and definitely important to you guys a s couple.

I would ask her to be one anyway. Like what PP said it doesn't need to be even

Either you can have one pair of two girls to one guy, or include her in a different way such as doing a reading in the ceremony.

You could have a groomsmen walk two girls down the isle as the last to walk through, one on each arm

Having odd numbers is totally okay! I wouldn't skip asking her just because of numbers

I’m in the exact same boat as you. My FH may ask her husband to be one of his groomsman but I feel like he is doing it just to make the numbers even. We are all good friends, but I am a lot closer to her than he is to him