You haven't said what kind of baby gate you're using - does it have vertical slats or rails? Grippy little toes can climb those pretty easily, but the mesh kind might prove a little tougher to scale. Worked for a bit with my climber, anyway. I think ours was Graco.
You might have to stop thinking gate and come up with another angle. Now that she knows she can get over gates, you might be pretty much screwed! :D
How about a Dutch door (top and bottom open separately)? You can still hear her and she won't be completely closed in, but it's definitely tougher to escape; just make sure there are no chairs or stools in her room that could give her a boost. Maybe if you painted a cute little scene on the inside bottom half, it could be like a TREAT to have it shut.
Or you could install an electric eye that chimes when she walks through the door after bedtime. There are probably lots of other solutions, but you get the picture - sounds like it could be time to stop thinking "gate" and go to a more general "escape prevention" mindset!
Good luck with your smart little climber!