RSBM
It probably has nothing to do with anything, and will not help any sleuthing efforts, but from quite early on, I have been wondering if this boyfriend was real, or just something about which she posted online.
I have no idea whether she or the ex-husband has been more guilty of, well, being a pain-in-the-backside ex, but one thing I do believe is that she has been obsessed with him and their breakup. She has been very vocal and posting publicly about it all over SMS.
MOO, as always, but she doesn't sound, to me, like a person open to an actual relationship. Would the boyfriend see these posts all. the. time. and be fine with his girlfriend being so preoccupied with her ex? Please correct me if I am wrong, but other than random mentions of him via Heather's SMS accounts (IG only, I believe) and maybe something by her mother in the very beginning, this alleged boyfriend was never actually seen by anyone?
Again, this is all IMHO, and possibly not helpful whatsoever, which is why I had never posted these thoughts before. This photo of Nashville where she, again, just mentions the boyfriend, has brought it up.