Some cats are just a bit temperamental. Even sweet cats often only want to be pet on their terms, and can get overstimulated sometimes. And not all cats like being held. If she's not hurting you guys when she slaps/snaps, and she's not escalating to biting/scratching, I probably wouldn't worry about it much.
Though, some people have offered good suggestions as to what could cause reactions like this, and it could be a good idea to ask about it the next time you take her in for a check-up, just to make sure everything's all right.
Also, when it comes to riding on your shoulders, she might be able to learn to hop on if she's up on something high enough, like a table, and you crouch down. I had a couple cats who were able to do stuff like that. One of mine, when he was younger, would walk onto my back if I bent over. Though, if she doesn't mind being picked up occasionally to be put on your shoulder, then that works.
Though, some people have offered good suggestions as to what could cause reactions like this, and it could be a good idea to ask about it the next time you take her in for a check-up, just to make sure everything's all right.
Also, when it comes to riding on your shoulders, she might be able to learn to hop on if she's up on something high enough, like a table, and you crouch down. I had a couple cats who were able to do stuff like that. One of mine, when he was younger, would walk onto my back if I bent over. Though, if she doesn't mind being picked up occasionally to be put on your shoulder, then that works.