Head canon that after they defeat vecna, Nancy gets super in her head about stuff and believes she’s the reason the people around her get hurt (lots of unresolved trauma and feelings from Barb’s death and the guilt from that). She especially thinks this about Robin, and she’s so scared of hurting her that she decides to slowly start pushing her away.
Only… it works much faster and easier than she thought it would.
Before Steve, Nancy, and the rest of the Party, Robin had some pretty shitty friends. She’s used to friendships ending because she’s “too much.” (Also for the sake of this hc, Vickie dumps her right after the battle because it’s all “too much.” We all know Robins mind immediately translates that to her being “too much.”) So really she’s just been waiting for Steve, Nancy, and everyone else to get tired of her and just stop talking to her- from her point of view that’s totally normal because she’s gone through it so many times. She’s honestly shocked they’ve all kept her around this long.
So when Nancy stops talking to her out of the blue, she just sort of… accepts it. Her first thought is that she’s surprised Nancy didn’t do it sooner. Her second thought is “when is Steve going to do the same?” But let’s not think about that too long…
Anyways, Nancy realizes pretty quickly that Robin didn’t fight for the friendship at all. She just let it go. And for maybe 5 minutes Nancy’s angry about it. She thought she meant more to Robin than that. But the more she thinks about it, the more she can’t shake the feeling that something’s wrong. Robin letting it happen just like that is so out of character for her.
And Nancy’s a journalist- we know she loves to solve things. So she starts paying more attention. Obviously the Party had get together every now and then, and Nancy goes out of her way to figure out from different people if Robin’s going to be there, and makes a point to drop by every single gathering that Robin’s at. So she notices 3 things: Robin side eyes her l the entire time, as if she’s waiting for Nancy to come and talk to her, and at the end of the night she’s clearly disappointed and trying to hide it; Robin’s quieter too, it’s like she’s scared to talk and when she does talk she looks nervously around afterwards as if someone’s going to deck her; she’s also stopped going to as many gatherings as before and is clearly pulling away from everyone.
So Nancy forms a hypothesis. And every worry about being bad for Robin, or Robin getting hurt because of her flies out the window when she realizes Robin’s been expecting Nancy to do this. That in Robin’s mind, she’s not worth caring about. And that alone is enough to snap Nancy out of her self-pity (not that her self-pity is bad or anything- it’s a very real thing to be scared of especially with all she’s been through), and she goes to find Robin and talk about it.
And knowing Nancy it’s probably at a super inconvenient time, so she’s sneaking into Steve’s house at like… 2 a.m. She eventually managed to find Robin’s room, bursts in, and is like “why the FUCK haven’t you been talking to me?” Cue Robin sitting up in bed, eyes bleary like “Wtf? What are you doing in my room? Also, you stopped talking to me??? I thought this was what you wanted??”
So then they have a very deep and tearful discussion about everything from Nancy’s fear of Robin dying like Barb did because of her (obviously Robin interjects to tell Nancy that Barb’s death is not her fault), to Robin’s belief that everyone grows tired of her and leaves eventually (cue conversation about Robin’s past friends, and Vickie dumping her). And basically Robin tells Nancy that she doesn’t need to worry about her, and Nancy tells Robin she could never get tired of being around her.
And then they realize they’re in love and make out.