"Can a guy and girl be JUST friends?"
My answer is a resounding yes, I have lots of women friends and my wife is not jealous or resentful in any way of them.
One is my ex-girlfriend before my wife, who has her own family of adult children now, we have been friends for 40 years.
Another is a woman who lives just over the road from us, both my wife and myself used to work with her, she is a single mum, and I go over for coffee and a chat nearly every day. We have known each other for 25 years now, and my wife is just as friendly towards them as me.