But jumping from the floor to the arm of the sofa...not so good. She kinda scrambles up. Or tries to, I think she was better at it when she was a kitten but now she's heavier and can't really pull herself up.
Ok, I have seen Sammie climb things in a rather laborious fashion when she could easily have made the jump in a half second. But she really likes climbing. Climbing is the thing she is good at. In fact, she has the talent for climbing down trees, which not all cats master. She can jump, and will when there is no other choice. When I started reading your description, at first I thought you just had another happy climber on your hands. But you mentioning she is having trouble pulling herself up, and that makes me think she may have some muscular, skeletal or neuro issue. Because Sammie's strength increased as her weight did, and is as climb-y now as she was as a tiny little kitten.
Also her whiskers are crumpled and some are broken off. I have no idea if that's related.
Any thoughts on what could be wrong?
The whiskers are a mystery. I have known them to get wrinkled up from exposure to high heat - like a curious kitty nose investigating an unattended candle, or a hot stove when I wasn't watching. I have known my cats to chew each other's eyebrow whiskers off in the process of social grooming (the bumps of the follicles feel like external parasites and get bitten). I have known one cat, an indoor-outdoor cat, who came home one day with her whiskers all cut off. She was afraid of strangers after that, so it's easy to chalk that up to human agency. A quick Google yields the results that medical issues such as nutrition and fungal infection can cause breakages. So yeah, it is worth bringing up to the vet.