advice :(

i know this is probably the wrong site to ask advice on but i think it'll help if i get some from non biased strangers on the internet.
i have a friend (let's call them d) whom i met thru a writing class. i've only rly started talking to them bc they would hover a little when i was walking back from class, like too close for strangers but too far for friends yk? one day i was like fuck it if ur gonna b this close to me might as well talk right? so that's how we became friends. i send d a screenshot of a text msg between me and my other friend (let's call them g) saying something stupid. d tells me they like g's name, and so could i introduce them? i kinda laugh it off and avoid it, bc i don't rlly like trios for the reason i always feel like there's always a duo in a trio and one always gets left out. me and g go out together often, so when d asks where i am, i say with g, and d would ask me again if i could introduce them to her, and i would avoid it again. one day i'm at the supermarket with g, and we want something but there's coconut on it which neither of us like. i ask d if they want it, and they say yes, oh ur out with g again, can u introduce us? i kinda laugh it off again, trying to avoid it, and they say "why do u hate me meeting new people?" and "wow you really hate me" and got really pissy about it (they occasionally said the first 2 things when i avoided the questions the first few times. they've also said those things when they've asked me to introduce them to other friends, not just g) and that they're sorry that they're being moody but they haven't taken their meds. i feel rlly bad and like i'm being selfish and unreasonable for not letting them meet, so i ask g if she wants to meet d. atp im rlly overwhelmed so i say haha i feel like im gonna cry. g thought d was a girl (they're nb, biologically male), but she agrees anyway (which i later find out is bc she was worried about me crying). the next day, they meet, and i find it...sorta weird. like d is being weirdly touchy with g, like smelling her, putting their head on her shoulder and then her lap, and patting it. even with me, they were sitting and took my arms and put it around their neck, and when i was laying down, they spooned me??? anyways after, g calls me, saying she was rlly uncomfortable with the whole thing, and now i feel responsible bc i was the one who introduced them. i talk about how i felt so bad i let d have their way while texting the supermarket, and g tells me i've been guilt tripped. she tells me i should cut contact, so i've been slowly ghosting d. the thing is, d and i r in the same writing class and for some reason, our prof wants us to write something nice for a person we've grown close to for the last day of class. i was thinking to skip but she says she's gonna email whoever hasn't wrote to anyone yet, so i've been worried about that. i just don't know what to do with d or the class anymore. i've told d a lot of personal info, and i don't think they're the type to go out of their way to stalk me or make me uncomfy or anything, but i didn't think they were the type to guilt trip me either, intentional or unintentional. any advice?