Hello,
Thanks for writing to Health Care magic, I am Dr , Muhammad Ahmad , I have read your question closely, I understand your concern and will be helping you with your health related problem.
According to your description of the incident and signs and symptoms afterwards , in my opinion your daughter's knee should be fine, knee is structurally quite strong and doesn't usally get damaged with normal intentional stretching .
I would suggest you to assure that she rests will...
cold sponge the area... wrap crepe bandage around it, apply some local pain killer cream if you feel like, you can get her take
Tylenol if pain is much, it shoudl get better with in 4-5 days if it doesn't then contact your doctor to get things checked up, currently in my opinion she doesn't need any emergency treatment.
I hope this answered your question, If you have more queries I am happy to answer you.
Regards.
Dr.Muhammad Ahmad