Hi Jay,
Rather than getting a companion, it is much more important to stop her from laying eggs. Cockatiels are notorious for becoming chronic egg layers in captivity. This is very bad for her health and will eventually kill her. In the wild, she would only lay eggs once a year, during breeding season. In captivity, our birds do not receive the environmental signals that make them stop. Cockatiels will breed or lay eggs when the days are longer, weather is warm, food is abundant and there is a safe, private place to nest. We have to reverse these conditions in captivity. Start by limiting her daylight hours to 8-10 daily by covering the cage early in the evening. If she eats a lot of fresh foods, stop offering those right now. Rearrange the toys and perches in her cage, or give her toys if she doesn’t have any – but no mirrors! Do not let her have anything she can shred like paper or cardboard. If her cage floor doesn’t have a metal grate, then even the cage bedding can be used as nesting material, so you may have to leave her with a bare tray and just wash it daily. Don’t give her a nest or anything she can use as a nest – no bowl, dish, nothing. The last thing you want to do is make it comfortable for her to nest. If she uses a food bowl, take it away and give her several smaller cups. If she nests in a corner of the cage, hang toys there to keep her from doing that. Move the cage to other places in the room rather than leaving it in the same place all the time. Moving things around in the cage, and moving her cage send her the signals that her environment is not stable enough for nesting. In some cases, a female needs to be seen by an Avian Vet and get a hormone shot or an implant. If you make the changes I described, and it doesn’t stop her from laying eggs, then she needs to have the shot or implant. Her body was not deigned to lay eggs year round and it truly drains her resources. When a cockatiel is overbred, it is not unusual to find her dead as she sits on her eggs. Her body will simply give out at some point. As to a companion, I would not recommend it. Even if you get another female, it can trigger more egg laying.
Thank you for asking Lafeber,
Brenda