Despite AWALT, girls are all random and all different. Some like you more than others. You'll have a different "relationship" with each of them. So fixing your problem with "this one girl" doesn't mean anything in the long term.
If you're in a LTR, then "trying to make it work" and "putting effort in" and "all relationships involve work and sacrifice" just means you are a variation of beta bucks. Even if you're not paying dollars, you're offering commitment and support by being a point of stability in her life and giving emotional support. And chances are she's giving you shit (or the sex sucks) and you want to improve your relationship.
Thing is... you can't change other people. Some things will help your LTR work better but ultimately you are not in control. She'll do what she does, and you have influence over that but you can't force her to feel something different to her actual feelings. And she'll act purely according to how she feels. That's never going to change.
The solution to your LTR woes is to fix yourself irrespective of her. Get some abundance mentality (or get it back), get more options with other women, flirt with more women, be more attractive, care less about your LTR and be less reactive to it. She's probably getting less sexual with you, respecting you less, while every year you're putting more and more effort into what's basically a sinking ship. You can't say a few magic RP words and have her sucking your dick like a trooper again. Doesn't work like that. It's your life, that's what you need to fix. Make choices that will work no matter what she does. Be more attractive, meet more people, lift some heavy shit once in a while, flirt with more women.
Conversely... if you're not in an LTR and you're trying to get with "this one girl", and you've not fucked her on two separate occasions, then she is nothing more than an option. Treat her as such. She might have boyfriend, she might hate men, she might hate you. I guarantee she has a whole load of stuff (good and bad) going on that you know nothing about. You can't take her seriously as a sexual option until you've had actual sex with her on two separate occasions. Until then - she's an option and nothing more. Don't treat her as the "one and only". Don't treat it like you're in a relationship that just needs a quick fix up. You're not anything to her yet, so do not commit excessive time, resources or emotional energy to her. And absolutely do not restrict your options with other women. You're more likely to get with her if you increase your options with other women. So if your question is basically "there is this one girl..." then your answer is "she doesn't matter, get more options".
If your question is "I find that every girl I chat up throws up when she sees me", then let's discuss your situation. If you have ongoing issues about how to apply TRP, what specific bits of TRP mean, then do ask away. If you have a situation that has come up that you don't understand, then ask away. If you want to know the best way to proceed with a specific situation then ask away BUT... ask from the point of view of "I'm seeing three girls but a situation has come up that I don't quite know how to handle and I'm curious on the best way forward".
Just don't ask us "how can I make things work with this one girl that I really want to get with". That's one-itis, it's trying to get control over one particular situation rather than having an abundance of options, it's putting too much effort and emphasis on one girl, and it's the perpetuation of the blue pill media story of the guy who makes a gigantic gesture to win the heart of his one super-special-snowflake-unicorn rather than fixing himself.
This is a slightly modified version of an article I originally posted on reddit's AskTRP forum.
I like this, Thanks