this happened with my DD (3) She's been dry in the night for a while and then suddenly began having accidents.
Always make sure she goes to the toilet before bed, no drinks on her bedside tale or up to half an hour before bed.
I think problems like this are often related to stress, so your impending house move could be troubling her and therefore contributing to the bedwetting.
Another possibility could be medical issues - a UTI for example, symptoms are not always obvious straight away, or if she's had one recently it may be related to that.
It's important to be reassuring, and not make a big deal out of it. Too late now but IMO telling her she'll have to go back into nappies if it happens again was the wrong approach. ( once it had happened a few times, I asked DD how she would feel about wearing nappies at night time again - didn't make it into a consequence iyswim?)
Sit down and talk to her, ask her if she's worried about anything and let her tell you in her own time.
I know it's frustrating when this happens after being dry for so long, but just go with it and give lots of positive reassurance. If she goes a night without wetting, give lots of praise in the morning etc.