Should I get a new playmate for my female after her other one died?

Question
I bought two females rats, cakes and blue, around 10 months ago but sadly blue died a few days ago due to a serious infection. The other rat has become subdued very quickly and rarely wants to come out and play with me. I wasnt sure how to go about getting her a new friend or whether i should? my local pet shop said if i get another one that she would fight it and advised me agaisnt it. So i just needed some more advise? thanks.

Answer
The pet shop doesnt know squat diddly about rats.  Females get along good with new rats, but you must do it slowly.  You will need to quarantine the new rat first for three weeks and after that, let the new rat live next to the existing rat so they can get used to each other. Each day allow them to meet, hold one while the other is loose in your rats play area. Do this for a few days and let them also go into each others cages to sniff it too. Finally, let them meet each other.  Expect them to sniff hard, wrestle a bit, but they should do fine.  Putting intact MALES togteher is more tricky than females.  Dont listen to pet store people. they just work there, they have no formal training on any of the animals they sell. In fact most of them are so clueless they cant even take care of the hermit crabs properly and if you asked them about a rats diet they wouldnt even know about high protein etc.... how many pet store people suggest a 3 week quarantine?  I have never heard of anyone being told to do a quarantine by a pet store employee.  They just talk about nothing but what they heard along the way.