It certainly is, but that's part of the deal when you step away from your parent's household and find someone to make your own with.

I don't expect everyone to be fully rational all the time, but some self-awareness on her part is needed here about habits she was raised with that may not actually be sensible.

If she really can't stand the temperature to be any cooler for her own comfort, then fine. The separate bedrooms seem necessary in that case, and if that means washing the guestroom sheets more often, sometimes that's the kind of price you pay for compromise.

It's actually often quite healthy for couples to accept they have differing "sleep lifestyles" and just do what's necessary to accommodate both, even if that means two bedrooms.