A housemate is not a random person. If you kiss her, it may be good, but it also may make your living arrangement more complicated in the future, precisely because she is not a random person but a non-random housemate. So you have to be careful. It may be good, of course, so you should not be scared of these feelings (in any event, having the feelings and being excited by something so tiny as a whiff of her hair means that you are very much alive, which is a very good thing even if you do not act on the feelings - it is like having a pulse and being able to breathe in that it signals that you are alive and well). But think through it - sometimes it is easier to keep housemates at a distance and have a more formal relationship, with scheduled housecleaning chores on rotation etc.