1) She techs and presses 6D while doing it. She flies out of range of 236D and can punish you for using it.
2) There is an 18 frame gap between 3C and 214D. Every character has a way to deal with it and I'm pretty sure all of them can do it on reaction. You should probably tell the people you play about that so they can start punishing you for doing so. 236B is safe if they block it and you can either 2A or backdash to try to get some momentum afterwards if you don't feel like just blocking (assuming they didn't IB it).
3) I wouldn't recommend using it outside of combos and the occasional 4B/3C mix-up from it. It is better to use jump cancelable moves.