How do I get my 3 yr old chihuahua accustomed to a new puppy in the house?

Cleo is a very sweet 3 yr. old but she is very unsure about her new chiweenie sister that is 3 months old. What is the best way to acclamate the chihuahua to having the other pup? Ideally I would love for them to play and cuddle together but I may be just asking too much. Let me know your advice.