Some other points:
Shella Snail has 180 HP - the most out of any monster
You can charge your charged heart & charged up attack at the same time & while doing other attacks. Because of this she can charge a heart while using a noncharged heart and make a barrage of projectiles with different timings and speeds on the screen. There is actually so much you can do with this, such as combo a crouch attack > charged heart > a lot of other moves, or you can jump forwards, then hold back while jumping so you can charge you move in the air while moving forwards. in my opinion charged heart is shella's best move. Sometimes it is important to move a bit forwards too however, because shella snail can easily get cornered and she is really bad in the corner.
One important thing to remember about only using projectiles is that you don't gain any pepper meter, so if you're trying to keep away your opponent at midrange, make sure to mix it up with a crouch attack every once in a while as well.
if you use up attack while dashing, you will keep some momentum. The slidy-ness of that momentum will carry over to the pushback your get if you hit an opponent, so if you're juggling an opponent in the corner with up attack, the best thing to do is to not dash in-between, as you will get sent flying away on your last hit. YEET
Despite being 3 hits, super attack can only hit 1 time, once you hit the first one, the opponent is invincible to the second one for a short while. You can hit a blocking (or parrying) opponent multiple times though.