Life can get pretty crazy and trying to impose a curfew on adults does feel a little demeaning. You might want to just have this converstaion with her, letting her know that you would like to see her every night, but you can't treat it like a mandatory checking in sort of thing. It should be just mutual.
If you need to know where she is so you don't worry, then tell her that. If you need to know where she is because you would rather she be home with you at all times and you need to know when she's going to be back...it's something else entirely.
For us we just talk all the time. We tell each other where we're going, how long we'll be gone (if we know) and what we're doing. I do it out of respect for my husband, because I think he deserves to know what I'm up to.