In regards to friends not noticing this sort of behaviour... This is quite personal, and definitely does not paint me in a good light. I'm not trying to give Tully a diagnosis, but I thought sharing this might show that sometimes outside of that particular situation a person can seem, for all intents and purposes, quite normal and well adjusted, but be batshit crazy within it...
I've spoken a couple of times about how I have BPD (borderline personality disorder), and in general I have always been prone to depression, but that full blown crazy that is almost identical to Tully's behaviour only came out in romantic - usually unrequited or instances where it was never going to work out for whatever reason. I had this one particular friend who I was obsessed with, and that obsession largely came about because there were unrequited feelings and I could not let that go. If he had feelings for me, chances are I would have forgotten about him in an instant. While we didn't have the touchy feely relationship, he was a VERY nice but insecure man, and did care about me. I started being able to confide in him things that I'd kept long buried and he listened and didn't judge and I came to completely depend on him for any sort of validation. Over time he and I grew very close, I would get jealous over the smallest thing and absolutely crack it, make threats (suicide, not always a manipulation tactic, sometimes it genuinely did feel like I could not cope without his undivided attention.) I somehow made him feel like I was the person who cared about him most in the world and like he would not know what to do without me in his life. He was constantly apologising for upsetting me. Almost identical to what I see happening with Drew and Tully. He was not the first that I behaved like this towards, but he was the first that actually bought into it and didn't just tell me to fuck off. It wasn't necessarily a conscious decision to manipulate him, but it was manipulation nonetheless and it worked. The thing is, I have friends that I have known for 15+ years, and I'm close to, but they've never seen me like that. It's not a conscious decision, but I've always tended towards being like that around people (men) that have no connection with my friends/family. All the while I knew what I was doing was wrong whenever I took a step back from it (and then I'd self harm due to hatred at my behaviour) but I had such poor emotional regulation that when I was around this person (and the men that came before him) I was overpowered by irrational emotional responses. It took a long time and a lot of therapy and medication trials for me to be able to break that and be able to have some sense if control over my emotions and responses, and whenever I've spoken to people that have known me (my family, friends) they are go smacked at my diagnosis because they've NEVER seen that behaviour.
So it doesn't surprise me that Tully's friends and family may not have seen this behaviour before, but I'd be very surprised if this is the first time it's come about. I'm not saying she is exactly like me or has the same diagnosis, but it's clear to me that she's troubled and doesn't surprise me that people close to her may not have noticed (or noticed the extent of it).
Ps. I hope all of that actually made sense!