Hmmm, I was going to suggest retaining liquids but you're already doing that. That has been helping my son out for a few months now. We'll still have the occasional accidents though, but he's not leaking out of his diapers, so that's a plus.
I know it sounds crazy, but what about urinary incontinence supplements? I know it's not all the time that she's wetting herself, but it may help her hold it at night?? Just throwing something out there.

I empathize with you completely! Diapers, diapers, diapers. There's no reason why she can't hold it after peeing before bed (unless medical of course). Seems like she may be getting rewarded instead of suffering a consequence (without you realizing it). You give her kind attention and a one-on-one time conversation when she wets the bed. Sometimes that's exactly what kids want, a chat.
I'd say either diapers for awhile longer, or when she wets the bed don't explain anything or be "okay" with it. Just give her a quick and brief "This is not good. You're a big girl and big girls use the potty." Also, the dvd "Potty Power" was a huge motivator for my daughter. (I know that this is an old post, but wanted to reply in case you were still struggling, or someone else needs help.)

Don't know if this would help, but our 11-yr old high-functioning ephew suddenly started wetting at night - we tried all the usual things - no liquids after a certain time, pee before sleep, wake up in the middle of the night, etc. Visit to the pediatrician got us a prescription for Desmopressin for 6 months, then weaned him off two weeks ago. So far, success. He still has his "last pee" before sleep.

He had worn big kid pull ups until about age 10, so if a prescription isn't appropriate for your child (too young, maybe), pull ups might save you all some sleep. There's no shame in it - especially at 4. I also got 3 waterproof, fairly breathable, and quiet mattress pads. One on top of the other, so when he was wetting, I could just peel on the first pad and go to the next one. Am still using them, in case wetting reoccurs.

We also have had 5-years of chasing bowel movement regularity due to chronic constipation. Pediatric gastroenterologist gave us support and a protocol to follow, and we no longer have smudges, backups, or accidents. It's much better now, but it may always be a problem.