Age out question

[john2005]

My parents who are permanent residence will soon fill the I-130 for my sister (who stayed back home.) She’s 19 year olds now. I know that she have to wait about 4 years to get her available visa, but she will be at least 23 at that time.

Is she still eligible for F2A at that time or she will be converted to F2B as soon as she turns 21?



Any advice is greatly appreciated.