K.M.
Wow! You sure have your hands full. Everyone says each child is unique and you are certainly experiencing that firsthand. It seems that, though they were born together, they do not require the same care. I would start by reducing her naptimes by 15-30 minutes for the first week. observe her behavior and adjust. You could also try pushing back her bedtime. A shift of only 15 minutes could do the trick. My adorable daughter had virtually given up her naps by this age, so count your blessings.
When she does get out of bed, get her back to bed with the least interaction possible. Don't let her play with toys. Put a special lightswitch cover on the lightswitch to keep her from turning it on. Use a reward system that encourages her going to bed and staying there. Don't leave out little man, though; if he's staying in bed, you don't want him to alter HIS behavior. Use him as an example (without saying so) by announcing his reward for staying in bed. It could be a special treat or toy. Whatever your kids covet should be their motivation.
Sleep is not always a simple thing to figure out, but you'll find the balance. Best of luck to you!