I do think that hefty of a pushup is a bit much, even if you need the cleaveage, but I suppose it lends to the outlandish proportions of comic women. Whether it actually works or not is up to the viewer, I suppose. I'm ambivalent about it. Also don't talk about her boobs, she's a real hero and a real human being etc.
I'm sorry you have to deal with back pain from giant awesome boobs, but please know that occasionally I get jealous of big boobs because apparently you can tuck your hands under them to keep them warm in cold weather. That sounds awesome as fuck.
But seriously, if they're giving you that much trouble or pain, it might be prudent to look into a boob reduction surgery.