When I was 16 I was 5'9'', 135-140 and about 10-12% fat. I was a sprinter, and ripped as hell. There's no way of knowing from her height and weight if she's fat. All we can do is verify that gravity is in fact pullin her toward earth. Perhaps take her to have her BF done. You may be warding off a disorder by presenting her with the facts.
Perhaps it is time to explain that 'soft' is NOT fat, and that 'tight,' 'hard,' 'cut,' 'ripped,' or whatever adjective you wish to assign to being fit is NOT "bulky."
As a father, now sounds like one of those rare and extremely valuable teachable moments. If she is open, be sure to use it for instilling the value of fitness and resistance training. Truly, this would be the gift of a lifetime.
I agree w/ the above... but lets also remember that at age 16 the body isnt' "fully matured" so defining one's self as "fat" at that age can really be a mind fuck before even growing into one's body. I'm 5'7" and have been about 140 thru my high school years and more around 150 since then. I competed naturally at 133 and otherwise haven't seen that weight since before puberty. At age 16 I think its more important to establish the right values as far as diet & training than to worry about actual numbers unless she's (or they) are in a sport or something where bf is desperately important. But then let's take a look at the number of professional women who HAD to be aware of their bf at that age and are now recovering (or still suffering) from eatin disorders and fucked up self image!!