It may be her hormones (yes this does happen) but when female cockatiels are unable to have a hatchling during a certain time each year, they become stressed. Also keep in mind that cockatiels are frightened easily , and are very territorial . This is normal . Also, your bird may be in nesting season, so she becomes extra hormonal and territorial. Well I hope this helped. Good luck.

Thanks for the help! :D

My bird did that when he developed a fatty tumor on his stomach. He didn't want anything near it. He was young, too. Keep an eye out and see if anything gets bigger. Keep trying. Be patient.

For some bizarre reason my cockatiel has stopped stepping up. She has stepped up every time we try since the day we got her, yet for the past few days she runs away from us like she is scared.

She's 14 months old if that helps at all.

Thanks!