If a child has never been dry at night it's usually because they are not yet physically able to. There's no point putting her through all these 'treatments' unless she is giving any indication of readiness.
I feel quite passionate about this, as I come from a family of bedwetters, and I remember the great distress I felt at my parents trying to help me. I just wasn't ready and I won't put anyone else through what I wnet through. Including my dc.
Dh's family were all dry within weeks or months of being toilet-trained, so my MIL expected the same from her dgc.
All of ours have been or still are in night-time nappies. When they showed signs of readiness we started lifting them. By readiness I mean that their nappies were still dry when we went to bed. Often they'd be wet again in the morning. But when they were consistently dry in the morning we started rewarding them. Not because it would encourage the child to be dry - it's out of their control - but because it boosted their self-esteem. Particulrarly for dd, who is on long-term medication for bladder control problems.
Ds1 was reliably dry from age 8, after lifting him for over a year. Dd's nappy has been dry every night for the past month, and last night she went to bed for the first time ever without a nappy (shit I'm crying as I type this). I'm so bloody proud of her - given the problems that she has had ever since she toilet-trained, and the consultant warned us not to expect her to be dry at night for many years. I know I said that it's outside the child's control, but I'm still proud! She's 6.
Backt to the point: ds2 is showing signs of readiness, with his nappy sometimes dry when we go to bed, so we'll probably start lifting him in the next few months. He's only 3.
So you see it varies from child to child. But there really is no point getting them or yourselves upset as they cannot do anything about it until their bodies are physically ready. You need to give yourselves all a break. Use pyjama pants, tell her it's not a big deal - she's tried her best, now you'll take a rest and try again in 6months/nest year/when she's 8/when you're all ready.