What specific year are we taking "pre-Flashpoint" Wonder Woman from?
Diana was slumming for some of them ...
Also, does Val get her horse in this encounter?
If we're not talking, say, "Diana versus Slade"-era pre-Flashpoint Wonder Woman, however, this battle is only competitive if Diana allows it to be.
Which, in character, she would.
I'm inclined to think the superiority of Diana in terms of speed and sheer physical strength is such that she could simply firmly and gently bearhug Valkyrie into submission at any point of her choosing, though.
She simply has to desire it.
(Assuming the lasso doesn't work on Val due to her Asgardian nature, of course.)