One of my chickens has gotten injured before and I couldn't find any place that would take her in for an exam. Do you think it is okay to get two more chickens this weekend?
I don't mean you have to take her somewhere for an exam.... I mean that you have to very closely look her over. Have someone help you if needed but you have to run your fingers under her feathers and lift them to view the skin underneath to look for puncture wounds or cuts or bruises, lift the wings and look closely under them also. Usually bite marks are on the birds back or from the wings back on her sides (because the predator tries to grab them as they are fleeing, usually) but you have to look over the entire bird to make sure no injuries are missed.
Cuts or punctures need treated immediately (search on here under the emergencies section, there are many, many threads on wound care), bruises mean the bird at the least will be sore and should rest for a few days, but it also means you need to watch closely for signs of listlessness, which could mean internal bleeding. Again, searching the emergencies section can help with treatment plans.
You haven't mentioned if you determined how the predator got to your birds in the first place... and I don't think you should get more birds until you have fixed any fencing problems or predator prevention issues which could put more birds at risk.
If you are getting more birds at some point, do you have a plan in place for quarantining them until you are sure they are healthy to avoid exposing your bird to possible illnesses? They should be houses in a totally separate area for a few weeks to make sure they show no sign of illness before you begin introducing them to your lone hen.... also, do you have a way of housing them separately if needed if they don't get along for a while? Introducing birds can be stressful for birds and often can result in fighting, bringing in 2 strange birds when your hen is still recovering from her experience may not be good for her, especially if the new birds gang up on her.