How to get over a gymnastics mental block?

hey so in November i attempted to do a roundoff back handspring and broke my right arm. I was able to do one since i was in 5th grade (i just finished 7th) and i was pretty good at them but i dont know what happened. I gues i just wasn't focusing. anyway, i was in a full arm cast for 5 weeks and in December i got it off and was determined to get my skill back. For the past 6 months i've been doing roundoff pop outs, back handsprings on the trampoline, back handsprings down the cheese mat, and round off back hanspings on an air track (a little bit bouncier than a spring floor). i have gotton to the point where i CAN do my roundoff back handspring on a flat mat but i just can seem to do it without my coach "being there". she doent even spot me she just stands there. but when she watches me on the onther side of the gym i can't do it. i'm starting to get really frustrated and annoyed at myself. any tips? i've tried visulizing myself doing it, singing a really fast workout song in my head and just not thinking about but none of those have worked. it seems that i've been gaining some skills that i havn't been able to do before i broke my arm. for example, i did a half on the trampoline without hesitation. it's just this stupid round off back handspring. please help!!!!