Divorced parents entrances help!

My wedding is very very soon. My mom and dad are divorced but are both walking me down the aisle. For the reception entrances, I was going to have them walk out together - thinking they can just deal with it for 30 seconds, no hand holding, but just walk out at the same time.

My dad (and my grandma and aunts) now tells me that he thinks he should walk out into the reception with his longtime girlfriend - he would be more comfortable with that and she’s helping with some of the payments. Although she’s been around for years, I really don’t know her that way at all. I immediately said no, everything is already set and I’m not dealing with the headache of changing things last minute. If I do this, my mom would walk out alone and I just think that would look SO bad and hurt her feelings.

Anyway, am I overthinking and being a bridezilla? What are some other ways I can honor my dads girlfriend?