You could, however, have said "I met some sexy and some happy girls yesterday".
Hi GWB, but I don't see there were two girls by this sentence.
The second sentence is grammatically correct.
Shouldn't it be better to say something like:
I met a sexy and happy girl yesterday.
I met a sexy happy girl yesterday.
It's very interesting!If you want to be very specific that you are referring to two individuals, one of whom was sexy and the other of whoam was happy, you would say:
I met one sexy, and one happy, girl yesterday.