Unfortunately the myth of them all being cuddly is perpetuated a lot. The reality isn't quite as 'popular'. They are prey animals and despite being domesticated that instinct hasn't been dampened down. There are some that like cuddles but there are also some (perhaps the majority) that don't.
If they don't like being held you will have to take it as it is, and at their pace. They may never like being held. If they wheek when they hear your voice/footsteps, come to the bars when you walk past, allow you to stroke them in their cage or eat from your hand then they
do like you. That shows trust, because to them every big thing will eat them. So know that they don't hate you. Try not to put 'human emotions' on them either. They are guinea pigs and show their trust in their way.
I have been lucky in that my four don't mind cuddles or being held. But they don't like being picked up and I never expect them to get used to it, because that's their nature. Having said that, I don't actually cuddle them much. Even when they were inside lap time became a rarity after a year or so. One of the girls prefers to sit alongside me rather than on my lap. SO when I used to take them out, I'd have her on my lap for a few minutes then just put her in a cat bed thing next to me. She prefers to explore and I accept that.
Accept them for their little characters and, as said above, the fact they feel confident enough to tell you they don't like something. That is preferable to freezing in fear/chase the predator away.
With regards weight, if she is still putting on a little weight each week and her heft feels okay then she's fine. Guinea pigs have different shapes and sizes (as with humans). So go by her body rather than her offspring. Was she small when you got her?
