From what you describe, this issue has become THE defining issue of her relationship with you.That needs to end. You say she gets through the day and wets but only slightly-- can you see what an improvement that is? If so, why does it still rule your relationship with each other?
You've let her see you cry, more than once I figure, and I assume you realize that it was not a good idea ever, right? Because that tells a child that mom's happiness is dependent on something the child can't really control, and that's not a message you want to send. Please try to think like she does, not like an adult does. She needs the message that this does not matter so much to you, because the message for years seems to have been that it makes mom so unhappy when she lets mom down.
She is indeed trained. She's wetting a little, not enough for anyone else to notice. Yes, it's imperfect and frustrating, but even more, it keeps her toileting in the forefront of how you and she relate. Again -- that may not be the case in your mind, but what is she thinking and feeling?
Having her in diapers at night sends her the message that you consider her a baby. Even if she is saying "I want them at night," isn't it possible that she says that because she's now so afraid of making mom upset that she'd rather deal with her feelings that she's a baby (which is a big upset for a kindergartener, who wants very much to be a "big kid") than to see you upset? You said she's in diapers at night because you can't trust her to stay dry at night if she can't stay dry by day; but have you actually tried letting her go diaperless at night? Tried getting her up late, before your own bedtime, for one last trip to the toilet so she's empty? That can help a lot -- parents hate to wake kids but it does help the child stay dry at night.
And in that long list I didn't see a mention of any visits to the doctor when she was younger to see if she had any physical issues that might be behind this. Have you? She might have a chronic infection, or this might be stress-induced, and some of that stress is coming from the knowledge that she must hide things from you because she upsets mom when she can't control her body.