As a (much) older live in nanny, I disagree with Artandco, a live in nanny should be part of the family, if you are cooking an evening meal, ask if she wants some or let her make her own alongside of you. Most weekends I like a lie in and to take my time to get up and ready to go out but two days a month I have early appointments so I have breakfast with them (or grab a slice of toast to eat on the way) Some weekends my bosses will have brunch and will text to say they are having xyz and there's plenty if I want some (usually after waking me with the smoke alarm!!)
House rules - as already stated, talk about overnight guests, family/friends is fine, they shouldn't have to ask but should let you know. No strangers to her (or him) but as a nanny I would never let someone I didn't know well and trust into my employers home, be that a new boyfriend, a nanny, a mum I'd met, or the meter reader without checking his/her identification with the company. Also, let her know if you are going to have overnight guests, it's not fun counting showers and then running for the bathroom to find a naked man already in there (no matter how gorgeous he is!)
To let you know if she's going away/not coming home, just so you can lock up properly, set the alarm, not worry. I'm 14 years older than my employers and obviously a grown adult and I can do whatever I want, however I know that they would worry if I didn't come home, it's just common courtesy to let them know.
Noise - you can ask that her tv/music is not too loud after xx time, when you go to bed. But also be aware when you are up early at the weekends to try to keep the noise down, don't let the children play outside her room at 6am! Or scream/squeal for hours on end (thankfully my charge has grown out of squealing but DB had to be pulled up about it, he said I'm up, everyone can be up, MB said fine, I'll bring him into our room on your lie in morning and let him squeal to his hearts content, he kept him quiet from then on!)
I also wouldn't call them house rules, it sounds a little condescending, like she's a child who needs to be told how to behave. Just bring them up in conversation.