Hi! Congrats on making it to 10 weeks! My DS is just a couple weeks older than yours, and we just went through something similar. I don't know if it is really a supply issue, though. Is she having wet/dirty diapers? I think that at this time a lot of things are happening. The baby is getting way more efficient, our supply is regulating, and the baby is getting a bit more distracted. I wouldn't supplement because that would definitely encourage a low supply, but maybe just let her feed more often for 2-3 days to give your breasts a kick start. Or, you could pump an hour after each feed. Even if you don't get much milk, the stimulation will tell your breasts to produce.
FWIW, I go to a lactation group where we have the option of weighing the baby before and after we feed. I did this a couple weeks ago when DS2 was doing the same things you are describing- on and off, fussing, wiggling, on, off again- and the weight change was 7 oz! He definitely has more intense feeds, too, so I feel like he is getting enough.
Check out the birth club groups if you can- there are a bunch of us with LOs the same age. I will see if I can figure out how to post a link