My boyfriend's 11 year old daughter asked me about sex. I answered to the best of my knowledge but, I didn't go in-depth. Shouldn't she be asking her parents about this?

Generally yes she should. But there could be a reason she is uncomfratable with it. Ask her why she won't talk to her parents. Also, keep her parents informed of what she is asking. They need to know
(unless of course you feel it would be unsafe for her to let them know, you didn't say anything about whether they are abusive, this could be a reason why she is afraid to talk to them)

Yes she should, but she may be uncomfortable taking to her parents unless the relationship is very open. As a teenager, mine wasn't.

One of the best things you can say is that sex=babies and that no form of birth control is 100% effective and that her parents should be having this discussion. You need to be able to accept the responsibility of child before having one.

Sex comes with a risk of disease, some of which are incurable and some making it impossible to have children if left untreated. Organizations such as Planned Parenthood are around to help.

Know the laws of your state concerning people over 18 and minors. If a BF doesn't respect the word no, move on.

Don't force abstinance, but rather make it an obvious choice.

Yes, she should be asking her parents about it.

Either that, or you should ask if it is something they are comfortable with you discussing with their daughter.

It's probably okay, but if you advise this kid, and information is seen as over-stepping your bounds, it could cause some stress between you and the parents.

I have to say I admire you for having an obviously good relationship with this child, as she is coming to you, and you are honest with her.

But, just to cover yourself, run it by the parents.