Sorry for your loss :C I lost my bird Gray who was bonded with my other bird Mcnugget around a year and a half ago. I looked in the cage he was fine then next thing I knew when I looked against I didn't see him. He was laying on the cage floor I took him out in my hands and rushed to a vet. He died in my hands on the way and I was heart broken. It took Mcnugget about 1-2 weeks to adjust and even after that he wasn't as talkative. I took him to a avian vet just to make sure he was ok and he was. He'd sing from time to time and had energy bursts. Now he is a bit quiet and chirps back at my other keet Pineapple when she chirps but he is a healthy keet. Though if the bird is trained and isn't afraid of you it may make it easier for the keet to adjust

I'd wait awhile to get another parakeet you can read my forum post " New Parakeet with old parakeet and cleaning". There are a lot of posts on it ,but illusive Fantasy (<----very knowledgeable) explained a lot of things to me. For now though I'd just give your bird time to adjust and bond with it. Then if later on you feel its time to add another parakeet to your family then go for it