Yeah, Kitty does this sometimes too. Obviously you can't see what's happening in there, but I get the impression she enjoys the let down bit as the milk comes gushing out nice and quickly, but then I wonder if it slows or even stops for a bit, as if I'm not using the SNS, she gets a bit stroppy and fidgety, tugging at my nipple (ouch!).
Is she definitely not eating when she's nibbling, do you think? Only I think I made the mistake of thinking that Kitty wasn't eating as she wasn't doing the frantic gulping thing she does at the start, but I wonder if she actually was still eating, only it was perhaps dripping into her mouth rather than flowing? I used to take her off after only 10 minutes or so, as I thought she'd finished, but I think I may have been encouraging her to snack. Not certain, but just a thought.
It's a funny thing breastfeeding, isn't it? Some times it feels wonderful but other times, it's scary as you really have no idea what the baby's getting.
Hopefully another moderator will be along soon to give you some more help. xx