WHY DOES SHE THIK THIS BUT EVERYBODY ELSE DOESNT??!!! I NEED AN ANSWER?

okay so im in drum line and i just started ( about 2 weeks ago) the day i started after that cl period i heard the snare drum captain (i play the snare) say that i suck .And the other day we're practicing and i try to play this part on the snare very fast so she plays it for me fast like i wanted to and then i tell her that i cant play that fast and she says ooor u cant play at all ( i accidentally say ya because i thought she was gonna say something else. And she said this 3 days ago 2 weeks since ive started playing the snare). So then i asked other people how good i am on a scale from 1-10 most said 7 or 8. How come she thinks i cant play when others think im pretty good. And does anyone have any advice on getting better on the snare like exercises (extra points for this one)