Gregorian, I had this same issue with one of my children. Once in a blue moon she was dry at night, but usually she wet the bed within an hour of falling asleep. She wet it again throughout the night. We had no success with limiting fluids before bed, having her use the bathroom before bed, or even getting her up periodically in the night. Our pediatrician said some kids do not outgrow bedwetting until age 9, and a rare few never outgrow it.
The easiest approach is to put her in a diaper at night until she outgrows it. Personally, I was not satisfied with that option, so I went with a bedwetting alarm. It is a device that clips onto the child's underwear and senses moisture. As soon as she wets the bed, it will sound the alarm and wake her up. Over time, it trains the sleeping brain to recognize the urge to urinate. Simply place a waterproof mat on top of her sheets for her to lay on, so the bed stays dry. Teach her to get up and change her clothes when the alarm sounds, then use the bathroom, put a new mat over the bed, and go back to sleep. We always kept a few waterproofs mats on hand, since she wet the bed several times a night. We also kept spare clothes in the bathroom for her to change into, so she wouldn't have to dig through drawers in the middle of the night. In the morning, have the child take all their wet bedding and clothes to the washer.
My daughter was a deep sleeper, so she didn't respond to the alarm at first. When we heard the alarm, we had to get up and wake her. But we made sure she went through the whole routine herself, of changing her clothes and bedding and resetting the alarm. Eventually she got the hang of it and could wake up to the alarm without our assistance. Then she started sleeping longer before wetting. Then she started wetting fewer times per night. And eventually she started having a few dry nights. Then she'd have dry nights several times in a row. After three months, she was done bedwetting. That is apparently the average for how long it takes to see success from using a bedwetting alarm. So if you are up for it, I think it is the most effective option for eliminating bedwetting, if you don't want to wait for the child to outgrow it naturally. Not an easy option, but definitely worth it, in my opinion.
If you succeed, keep the alarm. If they relapse, it is important to get them to start wearing the alarm again as soon as possible, to keep them from falling into the bedwetting cycle again. We went through that too! But it's been 2 years since we started using that alarm, and she is always dry now.