I have to say that for me, part of the charm of Remus/Tonks, at least in fanfic since we don't get much in the book, is that it's so...normal. Nothing in Remus' life has been normal, and now he has this girlfriend who likes him and wants to have sex with him and gets jealous when other girls pay attention to him.

I think he must be over the moon for her, too, so he's reassured when she gets a little bit jealous.