A 13 year old kitty is considered a senior...
It might be best if you hold her when you are sitting down.
That way, when she jumps down, it won't be as far.
Is she checked by your vet yearly?
It is preferable to have a senior check-up at least once a year if possible.
The carrying over the shoulder is no problem (Charlie likes being carried that way). But I try not to allow any cat or kitten to jump down from my shoulder. I either turn them around and put them on the chair/floor or sit down first and let them go.
Although cats won't typically jump if they think it's too far, they can get hurt jumping from high places. I would sit down when petting or crouch down when kitty starts wiggling.