The approximate condition of the car can be found out by passing a drive test on it, but this will not help you find out if there is a problem with the engine. Better to contact a good mechanic who will inspect the alleged car. Regarding whether she had been involved in an accident before, there are no problems at all, you can check her story at Free VIN Check of your vehicle | VIN History Report | VinGurus. When you have all the information about the car, then you can buy it. You cannot make hasty decisions here.
Such a hard question to answer really, but the simple answer is yes, a used rally car can be safe. Every rally car to this point that I've owned has been used. If you're not mechanically incline find a friend that is, if you don't have any friends that are, talk to people in the rally community and see if someone could help you take a look at a car with you. There's always things to look at on rally cars because of the harsh environment they live in. The biggest thing is knowing what you're getting into and if you can take care of things yourself.