It's probably a phase - her body growing.
Make sure the bed-time routine is SOLID...no changes, exactly the same every night.
Our oldest who's now 5 - we had to modify her routine a little to include going potty twice over the course of about 2 hours before bedtime. AND cut off drinks in that time period too. We'd remind her that if she wakes up and needs to go potty that she needs to get up and go potty. She'd say, "I use YOUR potty" I told her she can use whatever potty she wants as long as she used one.
If/when she wets the bed, don't make it out to be a big deal because chances are she already feels bad about it. I remember once our oldest had had a very busy day and was really tired. She woke up at one point, having wet her bed, and came in to use the potty. After that she went and tried to use wipes to clean off her bed, then told me her pajamas were wet. I asked what happened (and had already suspected), she started to get upset because she thought I'd be mad at her. Once I said, "Well, we need to change your sheets..." she said, "You're not mad?" I told her I wasn't happy, but I wasn't mad, it wasn't a big deal - it was an accident. She hasn't had an accident since.
For what it's worth....