Sorry, but Angie's vastly underrated. She's taken the force of an A-bomb at point blank....and it was mildly annoying, not actually harmful. Her offensive output is impressive too. And I'd also point out that she got the better of Cpt. Atom in their brief fight until Grifter sniped her with some special metahuman-busting gun.
She might not be quite at a herald level (but she might), but Iron Man villians aren't going to give her a run for her money....even ones as versatile as Mandarin.
Also, she's made of liquid machinery, and can make anything her advanced intelligence can build. Like a GL, but with liquid metal instead of green light constructs.
She's also been molded into an incoherent form and still survived. And has cut apart metas with atomically-thin razors. And has blasted and hung with high level brawlers like Cpt. Atom and Apollo. And has made roughly 30 duplicates of herself. And has made a construct that stretched across a city (a small-city-sized aqueduct that channeled water from a dimensional breach).
Engineer easily. Engineer is mid herald level. She's essentially a lighter version of Magus of the Technarchy who is Galactus level. Mandarin would be crushed.
Hell, I like Engineer's chances against Apocalypse or Superman.
I really don't know much about the mandarin and his capabilities other then from the cartoon. I know what the authority respect thread has on her and I wasn't all that impressed she didn't seem to have top tier strength or power projection abilities that put her above any of the class that is just below harold. so yeah i don't know who would win
She's not a power character though, she's a versatility character ... she can literally create microscopic replicas of herself with all her powers that can enter your skull and shoot you in the brain.
Mandarin has always been underrated even by Marvel themselves so Mandy for all intended purpose should win this. Aside from the fact that he is a genius himself