I went through something very similar. My wife and I overcome and she wants it again. I strongly believe these situations are fixable as long as she wants to want it more often. Communication as usual is the key - and the frustration you feel is causing you to communicate quite poorly.
Reading through your post I think you are a lot of the reason she doesn't like it. You have all these requirements for what is and isn't a valid excuse when the reality of it is "not feeling like it" is a perfectly valid excuse. How is she supposed to not feel forced when she knows you'll get mad at every rejection? How is she supposed to want to do it if she feels like you are forcing her? Your conditioning her to equate you asking for sex with a stressful situation. You need to stop that behavior today. Sit her down - apologize for causing her to feel forced. Explain why you got angry and say it is no excuse and you will not do it in the future. Mean it. From now on not in the mood is the end of the discussion - just watch some porn and you'll cool off fine. This is just going to keep getting worse if you keep getting mad. If you want to fix this you MUST now approach it as a joint problem with BOTH of you that the two of you will work to fix. You should tell get that too.
So now she doesn't dislike it - how do you make her like it? If you suspect she's lying about enjoying sex you need to talk to get in a very non accusative way and assure her she can share with you and you won't get mad. Figure out what she wants more of. A great simple question is how often does she orgasm? If it's not basically every time that's what you need to fix. More lady orgasms=more lady sex. Most women won't come from just piv so you are going to want to do a lot of oral or even better get a Hitachi magic wand - those are like easy mode for making women cum. Try giving her a first orgasm before you even start sexing her so you know she will get one. If she had body image issues tell her she looks beautiful and compliment her and ask her if she lost weight.
When you ask for sex and get turned down don't get mad, just smile and tell her you want it soon. Communicate honestly. You can do it.