For the first foal it may be a bit old. She may have trouble getting pregnant. If she is in good health you could give it a try, but don't be surprised if she doesnt get pregnant. They become less furtile with age.
22 is too old for the first time. Most vets don't recommend breeding your horse for the first time over the age of 15. They can still get pregnant, but it's hard on their body, and can be dangerous for them.
It wouldn't be if she were a broodmare and she was continually used for breeding but if its her first time I would deffiently say that is way too old there are to many things that can go wrong. Her age increases the chances of things going wrong and so does the fact that she's a maiden mare, put the two together and you've got a recippe for disaster.
I think it all depends on the horse itself. Seeing that the mare had had foals in the past is one thing especially if the mare is in good shape but for a first time baby? I don't know that I would recommend it. Get your vet out and check her out. He will be able to tell you.