Eh, I didn't mind it. I don't think it was supposed to be taken as that she really would have done the same thing, if she had Wanda's powers, just that she was trying to be sympathetic/supportive of Wanda at that moment. Which was consistent characterization, since they'd had her as being sympathetic with Wanda through the whole thing, including her thinking that appealing to Wanda's humanity was the only way to save the town. I can even buy her being able to empathize with Wanda easier than the audience could, given the story tells us that the people in the town had some kind of telepathic connection with Wanda, and Monica got that, only wasn't trapped there as long or as helplessly as the rest of the town.
Agreed that her role in the story was a little underwhelming, though. I guess we can't really complain though, since the show is called WandaVision -- the main characters are right in the title. Really if anything, Vision's remaining absolutely in adoration and devotion to her was a little bit hard for me to buy. If you say he wasn't a real person and never had free will, then sure. But I think he's supposed to have been real, so I think his being even a little bit irritated about the whole thing might have been understandable.