Oh, it's not, which is what made it a stupid boundary to attempt to set. That "boundary" is instead just going to serve to soothe my own peace of mind, so that I feel comfortable and confident in withdrawing from her when she stays out with OM until 2am (instead of frustrated and needy).
Last week, I used meetup.com every night to go out and do things-- and I had a great time, each time, but then I got home every single night to discover an empty apartment: she had stayed out even later with OM. In a way this was a good thing because it made me realize how much of my motivation had been hoping that she would miss me-- obviously she didn't care. I'm still looking for events to go to, but now I know that there's only one reason to go, and that's for me to have a good time.