Don't frame it like a 'Fanboy wants on set' kind of thing. Just tell her you want to soak up the atmosphere of what it's like on a day to day basis when it comes to filming a TV series. Make it a professional request rather than "I'd like to meet such and such'. If you do it that way, you will more than likely get a positive reception from your sister. Also, you can take it a step further and ask if you can 'work for the day' to get some hands on experience. Trust me, this will get you in the door and your sister will be happy to have you along for the ride as she will take pride in showing you the ropes.