Yeah, I see your point. One thing that made me think that way was Josy saying things like "my dad and Monica", but that can also be because she doesn't like her very much and says it to distance her from them.
Another point could be that having Monica in could have a nice "conflict" between her, Tommy, and the MC. It's not just the name, she talks a lot about her and her relationship with her and her father. It can be just background for Josy for sure, but I think there can be more. That's another argument, though. (And mostly speculation on my part).
...And if we add Monica into the story we could #CuckTommy in more ways. I don't care we haven't seen her yet, this isn't about looks
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