For me, it's the disjointed hitbox of jMP plus the ability to fly around whatever moves I do, use jHK and then go ham.
Dont ever use j.hk against painwheel, its a terrible move in the matchup because it has little air to air ability against people moving backwards and painwheel can easily ground or air armor through it.
If the painwheels are getting very far away from you, then the matchup does get bad for bella. Hug her like your life depends on it, because it does.
That said, bella has many caveats over painwheel:
Priority
Double jump
Easy anti airs
Easy answers for air and ground armor if the bella sniffs them out (excelebella/super her out of air armor, showstopper her out of ground armor) showstopper will also kill painwheels ground super so anytime painwheel gets even kinda frisky with the offense, you have REALLY good reversals to use against her, one of which converts to full combo and thusly a reset, and the other not so great dividends but basically beats everything.
The primary thing you need to do though is not give her space. That is the biggest thing by far. Yolo her down. Realize that painwheels primary advantages in the matchup all come from space.
J.mp needs space to beat bellas normals, stinger cancels need space to not get punished in startup.
However, not all is lost if you lose your spacing which is of course bound to happen. You still have the ability to empty jump toward painwheel, land, armor run and cancel that into DD. Of course you dont have to cancel into DD. But it is a good option to have on the table so that the predictable painwheel cant just see you wiff a jumpin and pressure you for free...
Make sure that if you wiff a jumpin against pesky flying turtle wheels, that you let her know via DD or excelebella that you know the score and that she is playing for the wiff (its all shes really got that is "safe" against an aggressive bella)
I guess i can annotate your match against icky if you want... There were some key spacing issues that i thought i saw you had in there that werent doing you any good.
And last but not least, pls pls pls make sure that you abuse the shit out cr.lk>MGR... It is an incredible tick and against painwheel specifically can make her SUPER PREDICTABLE since she cant super through the tick... She has to fly or jump which makes the OCCASIONAL excelebella tick extremely easy to make.
If she jumps and immediately air supers out of the tick... Thats just an issue of you being read. It doesnt mean to stop the tick throws.. Just measn to slow them down and go for baits more often... Which is what any reversal generally signals.
:)