Sorry your editors English is not as good as yours. She is right that scholarly writing should avoid colloquialism, but your usage of "eclipse" is wholly orthodox; the more specific astronomical usage is a mere product of the original broader meaning. Unfortunately, if she rejected "eclipse" as colloquial she could do the same with "dwarf." Also, "dwarf" may overstate the disparity you reference, which would make "surpass" better, and closer to the literal meaning of "eclipse.

Aeryns suggestion of "exceed" is obviously good also, but I slightly disagree with her second one: If it were me (which it is not) I would write it as you did—then realize when editing that "well" by itself intensifies "may," so adding "very" is just gilding the lily. My personal opinion is that, if any part of your sentence is too informal, it is "might (very) well," not "eclipse." That is not to say I see anything wrong with the sentence, only that I find it ironic your editor objected to an indisputably valid usage while ignoring a more debatable one.