Sounds fine to me. I think if your supply was decreasing she would want to feed more, not less. I would think it's the other way around, i.e. she's not interested in feeding as much, maybe spacing feeds out a bit as she gets older and eats more, so your supply is adjusting to that. Your boobs have been doing this for almost 10 months now. They know exactly what they're doing and how to do it, even if you don't. No need to worry