Do you think my sister has enough acting experience to become an actress on TV and films?

More than experience you need talent, confidents, hard-work ability, and an agent, and all that. However based on her age and resume I would say she could learn some monologues and try applying for agents, she might well be accepted and can then go out on auditions. Look in your phone book for agencies and remember they don't charge up-front. Get some headshots taken. Where do you live? It makes a lot of difference. Good luck. Email if you want to know more.