Lump either side under dogs jaw?

I noticed them a little a while ago and informed my Mum, who has this wait and see attitude about things, and thinks because theirs two, either side of her neck, they could be glands or something but I've not stopped worrying.

It's actually hard to describe where they are because they seem to move a lot, but they're either side of her neck, at the back under her jaw and seem to be the same size but they also change size, like getting smaller and then bigger, they're soft but not very very soft, so you can squish them a bit. you can feel them easier when she's sitting but when she's standing up/being active you can't feel them or when she's lying down out stretched.

She's only two so I'm very scared, obviously I'm making a Vet appointment regardless of what my Mum thinks (She thinks I worry too much which I suppose is true), she's insured so I'm not worried about the money or anything, I'm just wondering if anyone has heard/seen this before and what could be? I'm so scared for her.