Can a girl of 27 years old have stroke?

Yes definitely. Birth control pills and smoking also increase the risk of stroke.

My sister-in-law had a stroke when she was 27, and her doctor thinks it may be due to her birth control pills.

yes

I think you can have that on any age (I'm not a doctor though)

possibility.
even child can have a stroke.
it's all God job.
as a human we just trust our faith

sure can! Some of the earliest people in history to have a stroke were children, but that was rare and uncommon.Sometimes it can be hereditary or the way you take care of your body, such as bad diet and lack of exercise, or drinking and smoking. A stroke can sometimes come like a heart attack, meaning that you can get it at any age and anytime and not even know that you have had one.

Absolutely. Stroke symptoms are shown on link.

Yes, strokes don't discriminate by age or almost anything else. Every person's body respond differently to situation sicknesses your body may go through. Obviously if your a 27 year old women who is over weight your probably more prone to having a stroke but that doesn't necessarily mean they'll have one before some one who is the weight they should be. There is many variants but yes someone who is 27 can get a stroke. Just last year in England a pro soccer player died on the field while playing in a game, he was 21

yes.

Yes, even younger than 27 can have a stroke.