It suggests a couple of things.
First, that training does not accurately recreate the experience/environment of competition. Now obviously I don't know what training looks like, or what principles of practice design are employed, but ultimately if you want players who make good decisions in high pressure in matches, they need to be making decisions in low pressure training. If there is no decision making in training, they're not going to be making good ones in competition.
Second, it suggests that she is placing a greater emphasis on results (not uncommon in many players and particularly in teenage girls where awareness of being judged is incredibly high). Therefore some work needs to be done to understand her thoughts in competition as thoughts->feelings->behaviours, so we need to know what are the thoughts that are trigger the end behaviours. Best guess would be something around being judged, not wanting to let the team down, what people will say if I lose etc, but I'm speculating - that conversation needs to take place. She could even keep a little thoughts log and make a not at each change of ends of anything she thought during the previous 2 games (crucial to make it clear you or anyone else are not judging what she's thinking, only that you are building a picture). From there you can understand why and from why you can move into what.
Hope that helps.
