How do you tell a friend that they stink at something with out hurting their feelings?

I have a friend who is in tumbling with me.... I just moved up a level and now I am on the team! She got all mad at me when I told her that I am on the team. She told me that after she learns her backhandspring on floor then she will be on the team too. But I told her that she needs to do a back layout, backtuck, backpike off of double mini. Also she needs to be able to do a back tuck, back layout, whip, back pike, front pike, front layout, front tuck and stuff on tramp too... also the same with tumble track.....but she can barely do a cartwheel.....she thinks that she is good...but I really don't know what to tell her....because she STINKS.....HELP ME!