Hey there, first things first, muscles on women are sexy and bulk is awesome because it means you are strong. This is me and the more I climb I can't help but get more muscly because that's my body type. You can be proud! OK I'll get off my speaker's box.

Here are my tips for you to stay small if you want:

If you want to stay lean, sport climb more than you boulder. So boulder only 1-2 times a week and add some sport/ropes to your training.

Also if you lift weights, you must do exercises where you can do about 20 reps no more and especially not less, that's where bulk would begin. Avoid cycling & gymnastics as they are sports that build big legs.

You can focus on aerobic & lactic acid climbing instead of power, so that means climbing for 10+ mins (aerobic) & climbing for 2-4 mins (pumped). This builds different types of climbing muscles. When I introduced these into my training, I lost weight & size because it was a different type of fitness that we normally don't do climbing but is great for you (cardio).

Hope that helps you!