2 cats 2 different energy levels. Should I get my cat a kitten?

I have two cats. One female about 7 years old. She is laid back, loves a good cuddle and generally wants to be wherever I am. She doesn't LOVE the other cat but they share a double sided feeder, water fountain, living spaces etc and will sleep butt to butt on my bed. My other cat is a 5 yr old male and he has significantly more energy than she does. He is sociable and curious and loves to pounce and play. He often tries to play with his sister but as many older siblings, she wants none of it. He will jump on her from time to time which she very vocally expresses her disapproval. 99% of the time he will pounce and run off, or chase her and not attack. Ive only ever have to intervene once. It always seems like he just wants to play. So my question is should I get him a playmate, and how would this affect my not so social lady?