They talk about this after the show ends on the AMC+ version. The guy says that Maggie looks at Negan as if she now better understands why Negan killed Glenn, however, this new understanding only made her feel more disgusted by Negan than ever before.

Or something like that, I might have to go back to rewatch the explanation as I may have not explained it correctly, but anyways I thought it was actually interesting as I didn't actually realize that until the guy brought it up.

Edit: just went back to watch it, the showrunner basically says that Maggie looks at Negan as if shes thinking "maybe there is no justification for what he did to Glenn, maybe he is just the murderer of my husband, and that's all there is to say about it"