I think Its best to do this after Ragnarok officially comes out. I mean some people have seen it but for everybody to univocally agree with the feats, everybody has to see the movie.
*Warning Spoilers Ahead. Don't read if you don't wanna know stuff about Thor Ragnarok*
I had gone through the leaked plot a couple of days ago. Seems like Hela's basic power set is superhuman strength greater than Thor and she can conjure weapons? swords and stuff anytime, anywhere, any amount. Mjolnir Crushing feat seems to have context behind it, or not. Can't say now. Apparently Hela wielded Mjolnir before Thor was born. She was a superior warrior even to Thor, the best in Asgard but had a bloodthirst or something so banished by Odin. Mjolnir has already been confirmed to be made of elements from the core of a dying star. They probably mean a neutron star. Black Dwarfs and White Dwarfs won't have such dense and durable elements. It remains to be seen if she crushed Mjolnir by virtue of her strength or by some sort of influence over it like Odin. It's also revealed that Hela draws power from Asgard itself, so it could be influence over Mjolnir. But if it's her strength doing the work and if you assume Mjolnir to be made of Neutron Star material then that's a massive.. an unbelievable strength feat. She'd be able to literally crush anything in her hands. Neutron Star material is unbelievably dense and strong. Diana perhaps won't be able to deal with that kinda strength. She can deal with Hela's weapons in God mode though. She has this shield thing around her that disintegrates any projectile thrown towards her.