small skinny fingers don't seem to be a problem - check
THIS little girl's playing.
Some people with fat, stubby fingers can play a little bit too - as you can see
HERE.
A 7-fret stretch is unimportant and superfluous - the need to span that many frets is extremely rare. A 4-fret span will allow you to play 99.9% of chords, pretty much any scale you can think of, and plenty of lead guitar licks. I can span six frets, but the only reason I know that is because I just tried it.....I've never had the need to actually do it while practicing/playing.
The bottom line is that anybody who's willing to put in the practice and effort can play the guitar....it's not like all "good" guitar players are part of an alien race with perfectly shaped/proportioned, double-jointed fingers. The common denominator amongst good guitar players is that they've put excuses aside and practiced their butts off.
I think it was Henry Ford who said "Whether you think you can or you can't, you're right." That pretty well sums it up.