100% agree with JamieVardysHavingAParty "Don't encourage your teenagers to avoid condoms."
I think you need to be realistic that even if she is his first girlfriend, and even if he is a virgin (the two things not necessarily being synominus) there are no guarantees he won;t sleep with someone else while dating your daughter. So I;d teach my child the only way to stay as safe as possible from STDs is condoms and any boy not respecting that doesn't respect your daughter.
I'd also want to make sure she actually wants him to stay overnight, has she asked? She may not want that.
I'm well aware lots of people have sex for the first time quite young, but I think 17 is still quite young.
Plus if she goes on the pill now and doesn't come off it until she wants a family, that could be 10 or even 20 years.
This article suggests it is perfectly safe...
www.cosmopolitan.com/uk/body/health/a10316912/contraceptive-pill-how-safe-to-take/
but contains the phrase...
"Being on the pill is a balance of benefit over risk, and while the combined pill does come with some risk thanks to the oestrogen it contains - which can slightly increase a person's chances of getting a blood clot or developing breast cancer - for most people that risk is so minimal that it doesn't outweigh the contraceptive benefit."
These are things a young person will need to understand before just starting on the pill, surely. Making such decisions as young as 17 doesn't seem right to me, unless the person is mature enough to take it in and make a fair decision.
Anyway, these will be her choices, sex is an adult thing so if she is adult enough to have it, she should be able to make her own choice where and when and how it happens.