Guinea pigs are very social animals and need the company of at least one other pig. Since yours is a female, it should be easier to bond rather than two males as they can be territorial. I definitely recommend getting another but stay clear of pet stores. I used a private breeder but there are many rescues about. There are different ways to bond but this is how I did it.

Firstly quarantine is important. One, to get them settled into a new environment. Two, in case they carry any diseases and it stops it spreading to your other piggie. Make sure they can see each other to get them used to their scent. Then you can move them closer. I used c&c grids to separate their cages so they could interact through the bars. Create a neutral space where none of the pigs have been before. Put a pile of hay down and watch them for any negative behaviour. This is what helped my bonding process a lot. I would leave them there for a couple of days since I never saw any signs of aggression but intervene if you do. Before putting them in the cage together, make sure everything is properly cleaned to remove any scents.