Catabolic means it uses muscle, not builds muscle. (Like aerobic uses oxygen, anaerobic doesn't.)
Most yogis I've ever studied with were very lean, but since that's here in LA, I don't think that their skinniness came just from yoga. If you're very slight, you might want to build up some muscle through lifting and eating, as well as doing yoga. Obviously, big, huge BBing guys might have trouble with the flexibility, but most women shouldn't.
If you enjoy it, I don't see why you couldn't lift 2-3 days a week and use ashtanga as your cardio workout on other days.