Which character are you using? It depends entirely on which character you are. For Sakura: neutral jumping, ex specials both help. I don't know her well enough to give you enough answers, but a mixture of using your own projectile, neutral jumping, ex specials, forward + back dashing will do the trick. If you get to a point where you could normal jump in over their projectile and punish, there is a good chance they will stop. Punishing them once by reaction or their mistake should get them to stop, anyway.
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