I have a male cockatiel and recently got a new one she only 8 mns old and I think theyve been matin is that ok?

The others are not quite right about this. Yes, she is much too young to be reproducing. But obviously she is not too young to be mating. So long as they share a cage, (which is fine also) there will be mating from time to time and nothing you can do about it. You don't have to be concerned until eggs appear, if ever. You do need to make sure she is on a good diet including lots of veggies, leafy greens and don't ever let her run out of cuttle bone. The all important calcium can be the difference in life and death for a female laying eggs. So long as there are no eggs, don't worry about it. If she should lay eggs, "addle" them by shaking hard or by heating in a pan of water just short of boil. Cool back down and return to her. Don't buy a nest box. Waste of money. Just put her eggs in a shallow bowl lined with paper towels so she can keep them undamaged and they can tend them and sit on them as much as they want. Once they grow bored with it, they will abandon them. Only|||You shouldn't have been keeping them in the same cage in the first place, unless having them mate was your intention.|||I'm sure they think so...|||if you want a baby yes but other whys NO|||Breeding at that young can cause egg binding, which almost always leads to death, seperate them until she is older, after which it should be fine to have them together, I had a male and a female together and mating for 10 years.....then she got an egg binding problem, however, this isn't always the case. But definitely she is too young to be mating.|||Well--- not really because the 8 month old is too young to mate. It has to be at least 18months old so you still need 10 months to go. If they mate and have babies well the babies might have disease's or unhealthy so separate them!