"Despite herself, she loves this boy."
Translation:Malgré elle, elle aime ce garçon.
I think it's just idiomatic not to include "même" with malgré for this function. Examples:
I looked up malgré before answering this to understand how it is used. It seems that to say "despite herself/itself" one says "malgré elle" one never says "malgré elle-même", if you want to use the reflexive disjunctive pronoun then one can say "en dépit de elle-même", "en dépit de" only takes the reflexive form. This seems to be a matter of usage.
A nice website that describes this is; https://french.kwiziq.com/revision/grammar/expressing-despite-in-spite-of-noun-with-malgre-en-depit-de-nom.
Does this help? "soi" is impersonal : "one" in English.
Can any native speakers say whether this sentence is idiomatic French?
I find the use of 'aime' slightly confusing on DL. I understand that it can mean both to like and to love depending on context, but I have had answers marked incorrect in other modules for not using 'aime beaucoup' to mean 'love', having used 'aime' on its own. But here I was marked incorrect for using 'aime beaucoup'.