"What's nuts is that it's sometimes easier to feel feelings for a guy who's WRONG for you and essentially uninterested and unavailable than it is to fall for someone who's totally and completely in your life, present, willing, interested, invested, etc."
It IS nuts! I'm in a situation like that right now, where I've started seeing a guy that is really cute, smart, funny, interesting, etc. but on the other side I have a, ahem, guy on the side who is probably wrong for me for all the right reasons and yet I feel like I'm more interested in that than the one I know I sould be pursuing. I guess I'm concerned that maybe the natural attraction just isn't there as much for the first guy, but I don't know! It's also probably way too soon to tell.
But be comforted, LW, you are not alone.
I've been in a similar place before, so I completely sympathise. Although this is not exactly the same, I'll explain: in college I had a friend who I introduced to my social group. Before this she never really drank alcohol, which we did, to a respectful amount however. She pretty much went overboard with it. I don't know if it was to fit in (none of us drank THAT much) or to deal with other personal issues. Anyway, she really put herself in some scary situations. We kept helping her out even though I started to feel that I was enabling her to continue this behavior, while everyone else just went along with it and was afraid to say anything. I even thought her life was on the line! Eventually, I pulled her aside and told her that I thought she had a serious issue with alcohol. She brushed it off. So I told her that I was refusing, from this point onward, to help her if she was drinking, because I felt I had become an enabler. She did not take this well. And neither did my friends. I became incredibly frustrated when my group would continue to put me down for trying to save someone's life, while they continued to put up with her dangerous behavior. So, I ended up having to cut out a lot of those friends. In the end, I was at a party where she was also, drinking like 5 Steel Reserves in a matter of hours. I was told to leave by one of the old friends to avoid an altercation but I was completely sober and knew I wouldn't let that happen. She was put upstairs in someone's bedroom at the party to sleep it off, but ended up trashing the room in a drunken rage (not sure what caused it) and vomited all over the owner's belongings, as well as other things brought by guests of the party. It was such a disaster that I believe it shocked both the girl and the group of friends. I still didn't rekindle any type of relationship with any of them after that, but I did feel a lot of resentment afterwards, and some today, about how I was treated.
Point here is, it can take awhile to realize that a group of friends you have, not matter how it was in the past, could be detrimental to you. I know at the beginning you talk about how everyone else is awesome except for Jessica. Then why don't they understand how you feel? Why are they defending her? Just some thoughts on the matter.
It REALLY does help when you can finally let go. Even if you can't process and acquire everything Polly outlines above, in the end you can tell yourself "It really doesn't matter." Because, well, it REALLY DOESN'T MATTER. It does hurt at first for awhile even when you tell yourself that but with time and acceptance that IT DOESN'T MATTER you will feel so much better and more open and willing to accept new people in your life.