real quick Dog, I gotta go:
yes get a foam paddle float for cold water. You don't want to waste time blowing one up.
Foam ones pretty much have to be on your deck. Front deck preferable to rear deck - leave the rear deck clear for rescues! yours or helping someone else, like your gf.
PolarFleece, UnderArmour, etc. all have insulating qualities while wet. Some fleece is better than others.
Depending on your gf's height, weight, inseam, etc. your current boat may be way too big. It's a big cruiser. She would need to be an exceptionally strong and efficient woman to power one over any appreciable time or distance.
I am female, I understand female priorities in boat fit. Shoot me an email when you're ready to help her move into a SINK.
Some poly seakayaks can be paddled effectively on a pace w. most fiberglass boats - it all depends on the design, and the paddler's motor & technique. So don't dismiss a poly seakayak for her just on that basis.
CD Kestrel SOT is a really nice SOT - but she's still not going to be keeping up w. you - even at a very moderate pace. SOTs are wide, high volumed and slow with the exception of something like a CD Zone, an RTM Disco, maybe a Heritage Seadart (no longer made, and the Zone just got discontinued too) and some ultra high end ones made in South Africa and Australia
I am in construction too (commercial) and yes it sucks now.
P.S. why are you buying her boat LOL? Is she not an independent woman w. her own likes and income? Men buy me dinners and flowers, which is lovely & appreciated, but I buy my own boats and gear, thanks!
Seriously, if she invests in one she'll be more invested in learning.