16 year old girl, smoked for around a year and a half, is it possible to have got any form of cancer, or just increased the risk?

Both are possible: Just quit smoking while you still can recover completely. Smoking may ruin your young body and mind (drug dependency)

Doubt it: If she really stops, the lungs should clean up nicely within 1-3 years and look inside as if she never smoked. Everyone can eventually develop one or more types of cancer in their lives. Stopping this young after a brief smoking exposure removes most of her risk for this type.