I have a parakeet but I dont know if to buy another one because she has always been with other ones just that they passed away. Do you think I would need to buy another one?

So I should be with her for a few days and then if she is still sad than I will get her a new friend and thank you.

I would ask the staff at the store, but nobody/likes to be alone,

Not necessarily depends if you can be her new companion or not. However I would judge based on her if she seems depressed and is warming up to you, then u may want to get her a little friend like her. We all like to have someone like us to be with:)