I may need to start a radar gun calibration company...sounds like there might be a lot of business.
Let's just clarify the discussion. The average pitching speed is going to vary significantly depending on the level of play at any age group. You cannot define a meaningful average of all 14u pitchers (or pitchers at any age group) without specifying the level: Rec all-star, travel b, high school, travel a, elite regional, elite national, etc... For those who are able to speak for both their own experience, as well as everyone else's it might be hard to convince them of the true speeds being seen at higher levels, but I can tell you that we faced a pitcher from the Beverly Bandits Futures 12u last year who threw 60 mph consistently in warmups and in the game. That same radar gun had our pitchers throwing on the lower end sometimes of what we expected last year so I'm going to say we were probably getting pretty honest readings. You have a poster on this thread with a 14u daughter throwing 60+ mph so it is not the rare event or mis-calibrated gun, as some are implying, to see 60 mph at this age group, let alone upper 50s. I do think, however, that the number on the radar gun is going to vary less due to the calibration and more with the tournament or event you choose to use it at. I'm pretty confident in our radar gun and the numbers I posted earlier.
Secondly, to the OP... your daughter's success will always be defined more by her knowledge of pitching than by the radar gun. I have seen pitchers with "sub elite" speed dazzle at some pretty high level events because of their ability to: (1) Throw any pitch to any location (2) Throw any pitch at any count, (3) Have a true understanding of "setting up" a hitter. Sure, your change up may be killer, but if they know that by the 6th inning and we have a situation and a hitter set up for the up and in fastball, can you take the challenge and deliver it with a full count?... that's what wins games... not a speed on a radar gun.
Lastly, there are plenty of pitchers that get D1 opportunities with a 58-60 mph pitching range, but just usually not at the higher level schools and less as a starter (more as a situational type pitcher). It's not that the coaches have "forgotten" something or "don't understand" something... it's because the highest level hitters are so good at what THEY do, that it is just hard to beat them at lesser speeds (even with good location and movement). Again, at 14u, if you want to beat the best programs out there, you better have a girl in the circle with good pitch selection, good location and throwing 57-59 on average... less gets hit way too hard. Now at the high school level, a girl who really understands how to pitch and set hitters up, but may have just average speed can be extremely successful. Keep finding ways to challenge your daughter irregardless of what the radar gun says and if she is a gamer, she will rise to the challenge and find ways to win games.