Mychael, I agree with Jimmy. If it were me, I would dress to please her.

I hate wearing ties, but if I'm to go to a function where a tie is necessary, I will wear one.

When my older sister was married, her husband (who hated beards) required me to shave to come to the wedding.
That I refused, I've had a beard not for nearly 35 years.
Trousers are different, you can change out of them when you get home.

That my advice.