Well the pet rat lives to 4 or 5 years of age. So we are talking about half of this rat's life has already passed. If you got a new 'young' (I doubt you could handle a baby and its needs) rat, then you are looking at that rat being left alone 2 to 3 years down the road. All things die in their time being the problem. How is the rat lonely? I mean did she speak to you and say "Gee I wish I had a friend."? Or has her behavior changed recently indicating depression or something along those lines? If the first then by golly you best better get her to Hollywood - she'll be the star of many talk shows and have a global audience and lots of fans to be her friend. If its the other then I suggest taking her to a vet since many health issues can lead to changes in behavior. Rule out health issue prior to a radical change in her life like bringing in a 'new buddy', if shes sick or in pain a 'new friend' could be disastrous for both her and them. Once health issues are ruled out then I suggest you speak to the vet about how to acclimatize a rat with a new rat. I fear that a rat who has been the lone rat in the household will not get along well with new rats. In fact more often than not the older rate will fight with the new rat, or will be terrified and will not 'socialize' with the new one. http://www.ehow.com/how_2043709_new-pet-rat-another-rat.html might be a good start - mind they point out right at the top that it mayn't work out.

shes just really excited when i open her cage and she sleeps all day i just got an idea wat if i got another 1 or 2 year old rat

I don't know much about rats but check this out. http://www.wonderhowto.com/how-to/video/how-to-raise-rat-or-mice-as-pets-or-snake-feed-237