Alright, so this may be controversial, but I actually think this was a much needed realization for Marin. We know that Gojo would likely never voice for his own desires, as that just isn't the kind of person he is. Marin is way more extroverted and will always choose to "fill the void" with something she likes to do, or wants to do with Gojo, whenever they had finished a cosplay project.
This finally made her realize that Gojo isn't just her personal tailor. He still has his own dreams and wishes, all of which has gone to the wayside for the past while so he could focus on Marin.
This is pretty much textbook behavior for Gojo's personality type when they are paired up with an extrovert. They either lack the self esteem, are too timid to ask to do their own thing, are too considerate for their partner's enjoyment to stop them from doing whatever they want to do and focus on what s/he wants to do, or worries that asking for "their turn" will end their relationship/friendship.
So I am glad to see that Marin finally is recognizing this, and I am hoping she doesn't go overboard with her "follow up". She doesn't need to drop everything and do whatever Gojo wants, no matter what it is. That is wrong, and not what Gojo wants either. All she needs to do is tone it down a bit, let Gojo breath for a while, maybe take a cosplay break or he'll, maybe do a doll themed cosplay for Gojo.
But I honestly think that Gojo is the kind of guy who would be the most happiest if all Marin did was just come over and be in the same room as him while he does his doll work. She doesn't have to constantly talk with him either, just being there, silently reading or on her phone while just casually sitting on his floor or bed would be perfect. She doesn't need to be his audience, or take a fake interest in dolls just for his sake, just being there and being his supportive friend/gf is likely more than enough for Gojo.