I just wanted to add something ancedotal here, even though I am not quite caught up on the thread because I'm reading the posts about why would Heather cry on the phone to Bri or why would she call him over & over etc.
Ten years ago when I was in my early 20s I began seeing a man who was in his mid-30s. He had recently separated from his wife and as far as he would tell me he was free to date, but let's just say that that was not really a mutual understanding.
To cut out a lot of unnecessary narrative I'll say that I can understand more or less everything we know that Heather did. Every time I would try to move on from this awful love triangle, up he would pop with the I miss you & I want to be with you. It was so hard. I hated the drama with his wife. I hated feeling like I was being played for a fool, but at the same time I was in love with him. It was intense. I didn't want to be apart from him, but I would remove myself, try to move on and get sucked back in with an out of the blue late night phone call. So, IMO of course Heather would have willingly left the house to meet with him. Of course she was upset when she called Bri. It takes so much emotional work to move on (and maybe she wanted Bri to know he's calling her and saying this stuff because your friends care about you but they are so condescending when they're not in the sitch "he's obviously playing you, move on" etc. it's vindicating in its own twisted way).
Maybe those phone calls were rage calls "what the heck is with calling me and saying that and not calling back" or whatever. You get so wound up your pride goes riiiiight out the window. You can be exhilarated & angry.
TL; DR I don't question or puzzle over any of Heather's actions because I've been there. She wasn't over SM (IMO), but she would have got there.
Luckily for me I wasn't involved with a couple of psychopaths, and I was able to mend my broke heart by road tripping across America, where I met with a friend of a friend who happened to be a lovely Georgia boy & we fell in love over the next few months and are together to this day
(I just wanted to add my happy ending, as Heather was entitled to one and I always think about her now when I think back on those days of my own)