User blog comment:Gcheung28/DC Heroes vs. Villains Bracket Tournament - Round 3/@comment-206.131.133.68-20141009150850/@comment-1038387-20141010111950

She's not invulnerable, she's just way more invulnerable than average. Byrne retconned it, I think, into surface area - projectiles with a smaller the surface area could hurt her. Like bullets and arrows. That's why she has to deflect them. But a punching fist, which has its power spread over more surface area, not as much (except when it's a superhuman strength punch, of course). But she's still durable enough to recover from it.

Naturally, she's also vulnerable to god-level magicks. But everyone is.