Dogs become socially mature roughly between the ages of 2-3, and as a result, we fully expect some changes in their behavior. Typically, we should expect our adult dogs to play less in general, be more selective about who they will play with, and be less tolerant of what they consider rude behavior. Why should dogs be expected to play with every other dog who shows up or to put up with rude behavior. Dogs who are hurting often respond with what looks like aggressive behaviors, telling other dogs to move away is a reasonable response if getting bumped or jumped on hurts. Undiagnosed pain is often the source of behavior problems, and treating the underlying issue - or merely treating the pain - can often help dogs be more tolerant of other dogs. Fear is easy to install in animals and it can be difficult, and sometimes impossible, to resolve, and dogs can become afraid at any age. If your dog is healthy and not afraid, it’s absolutely okay for her to simply not want to play as much.
I’ve seen dogs who haven’t been able to socialize - for any number of reasons - get a wee-bit out of practice, they might be a little too forward or they might be a little more timid than they used to be. Given the last year, many dogs haven’t had as much opportunity to interact with other dogs, those dogs might get rusty social skills, or they might be just dying to say hi to others of their own species. We often see these dogs pulling, growling, barking, and snarling at other dogs when they are on leash and come upon another dog, but these dogs may simply be frustrated that they can’t get to the other dog to say hi.