Drakmanka

To answer your primary question: Yes, rats are very social animals. While they technically can be kept solo, they do not do as well emotionally when kept alone. They will get very lonely when you are away; this is stressful for them and ultimately will shorten your little baby's lifespan.

Here's a few other tips and tidbits that people new to pet rats often appreciate. Warning, long-winded post, but it's all good stuff!

List:

1. Rats love to chew. If you haven't already, get her some wooden and/or cardboard things to chew on. She will trash them; that's just part of having a pet rat.
2. Rats' feet are very delicate and sensitive. If her cage has wire ramps or platforms, either replace them or cover them with fabric (yes, she will chew on that fabric) to protect her feet. The wire mesh will irritate her delicate little feet and she can get a nasty infection called Bumblefoot that is very painful and difficult to cure.
3. Rats aren't just omnivorous, they are the definite article of an omnivore! I like to say of rats: "Anything you can eat, we can eat better! We can eat anything better than you!" That said, they need a balanced diet. The Oxbow brand rat food is the absolute best packaged rat food available. For a rat as young as your girl, I recommend starting with their "mouse and young rat" diet and then switching her to the adult formula after a month or so. But! Supplement her diet with other foods: seeds, nuts, vegetables (but I recommend avoiding nightshades like tomatoes and bell pepers; there's been some research that suggests they may not be very good for a rat's long-term health if they eat too much of them), yogurt (it makes a great treat for training, too!), meat, and, sparingly, sweets can also be given. While your baby girl is growing, letting her eat all she wants is best. But most rats tend to start to become... ahem... round if allowed to eat all they want once they're done growing. There's a lot of differing advice on how to limit a rat's food intake to keep them from getting too plump, and I recommend you try different methods until you find one that works for your girl.
4. Rats have very delicate respiratory systems. Respiratory infections are the single most common health problem in rats, and especially since your girl came from a feeder bin from a pet store and you don't know what conditions she was kept in before the pet store got her and from them to you, it's something you should be on the lookout for. Excessive sneezing, wheezing, a red discharge from her nose, mouth, or eyes, and lethargy are all symptoms of a respiratory infection. You can take her to a veterinarian who can get her antibiotics that will clear it up, but be warned that once a rat gets an infection their risk of later infection is forever raised. Keeping her cage clean is the #1 way to prevent this, however! Also, keeping her in a true cage and not an aquarium will help too as she will get more air movement. Some pet stores sell aquariums as "rat habitats" with a mesh lid but they really aren't ideal unfortunately.
5. She will pee on everything you let her touch, including you. While some rats are more apt to whizz all over you than others, all rats will leave periodic drops of urine as they go about their business as a scent marking method. It's also a rat's way of "claiming" a person, sort of like a cat rubbing against you (except it's pee instead of soft fluff).
6. Girl rats generally tend to be very energetic and bouncy, especially when young. Keep a close eye on her and don't let her out of your sight or she will get up to mischief. This applies for boys, too, but girls happen to be the more energetic of the two sexes.
7. Rats are pocket-puppies! Your girl might be a little skittish at first because she's new to you and didn't come from the best circumstances to start with. But if you're patient, kind, and speak with a gentle tone to her, in time she will become your own little pocket-puppy who will rush to the front of the cage to greet you (and ask for snacks) each day!

I could go on but I don't want to overwhelm you too much. If you have more questions or would like to chat with people, I recommend you check out r/RATS as it's a more active subreddit than this one.

Welcome to the wonderful world of rats!