Some advice from Seasoned Aupair mums - TIA

I was an aupair when I was 18 and yes for some of the year I had a bf. My family always told me if they needed me to work a weekend as I never hardly had to and I was always given plenty of notice, though having said that I knew I was expected to work so that had to come before spending time with him.
As for worrying about her spending time and staying overnight with her bf, no you shouldn't be worried not to be nasty but its not really any of your business unless it affects her working time. She is 19 and like you said that does make her an adult. You shouldn't have to feel like you have to watch her and her parents were way out of order asking you to look after her. She is employed by you to look after your children, not for you to feel like you have an extra child.

My dd is 19 and is currently au-pairing in Spain. I am naturally concerned about her but nothing she could do would top the trouble that I got into as an 18yr old Camp America student. I don't hold her Spanish family in any way responsible for what she does in her personal life. I do though consider them responsible to take care of her when is in the employment and look out for her health and safety, to feed her properly and allow her time off and privacy etc.
I have also had a Summer au-pair here for the past 6weeks. She's been excellent in all ways so I can't give advice yet based on her behaviour.
We have a new 19year old au-pair coming to stay next week for the next 6mths and she looks and sounds far more of a little minx than this one.
It makes for an exciting household.

The benefits of them having a boyfriend and getting out of your hair definately outweigh the cons.

We have always set out the following rules:-

1. That they tell us if they planning to be out all night/all weekend so we know not to be concerned/not to cook dinner for them and so on.
   
2. That they can have their boyfriends over to stay only once we have met them, and that they let us know in advance of every single ocassion that they plan on having them over.
   
3. For weekends you really need to set out a clear line in the sand - if you don't, you will never get the cover you need and they will 'begrudge' giving up their weekends. I reckon that you should agree with her that she does either two or three 'weekend' nights (ie Friday or Saturday or Sunday) each month, and that you agree to always set these out at least a month in advance, and that she agrees to let you know well in advance what days she definately cannot do. If you agree in those kind of terms then you should be ok going forward. Otherwsie you will find she will disappear from Friday night till Monday morning and you will never get weekend help..

agree with squiffy on everything but bf sleepovers. if they want to spend the night together fine, but not at my house. I don't want unknown man in house with my children. Watch out for bf staying more and more if you agree to this. You may find he ends up in your house more than you would like. And if you say yes this time it will make it twice as hard to say no to the next bf, who you may not be so keen on.

I have had 2 au pairs who have had boyfriends. The first was 26 years old and very responsible so I didn't feel that I had to know where she was all the time. Having said that, she always let me know. babysitting always came first, but it was never an issue with her. We got to know her boyfriend very well, and at the end he stayed over at our house sometimes.

then I had a 19 year old au pair with a boyfriend, and I felt very responsible for her. I asked her to let me know when she wasn't coming back and to keep her mobile on her. unfortunatly she completely abused our relationship and stayed out all night or very late all the time. babysitting was never an issue though - if I asked she would do it, regardless of her arrangements (she would go out after we got back anyway )
I think your ap is being unreasonable commenting on your sept arrangements - just say that you will give her as much notice as possible.