if a girl wears a size 14 and weighs 100 lbs, what size boys shirt will she wear

Well my son is thin at 85 lbs and no breasts, and the 14 is perfect. I would say if she is small breasted the size 16 would probably fit. But if she is large breasted I would go with the 18. This is only my opinion. I do not know for sure since my daughter is 14 and athletic and weighs 130. She does not wear the French Toast. She uses the XL in youth from Solo Wear.

If a girl wears a size 18 and breasted, would the 16 husky be able to fit?

I doubt it very much. The husky is shorter that the average shirt. A busty chest may make it even shorter than what is desirable

Which one will fit to a 17 year old?

It depends on the size of the 17 year old, A big 17 year old will need a larger one, but a slighter, shorter, thinner 17 year old may need a size smaller. I hope this helps. Your question left some doubts about just what size would be right.

difference in standard size and husky?

The husky size is about an inch to an inch and a half larger than the standard size. Ex: Size 12 (Standard) has shirt length of 25" and the Husky 12 has a shirt length of 26.8" Victoria- LT Apparel