This is 100% perfect wife material. Especially if she does it with passion and without hesitation. Ideally, she would even do this whether her husband was there or not, and better yet, if she were to get pregnant with another man. Any husband would be lucky to have her.
I used to see my wife in this same sort of situation almost daily. She loved being shared at every opportunity, and enjoyed the sex as much, or more, than her partners.