5 y/o bed wetting again

My oldest is 5 1/2. She was potty trained at 18 months and night potty trained by 2. She almost never had a slip up. Then when she turned 4 we had our second baby and my oldest started wetting the bed again. It has been iver a year and she sets the bed every night. She didn't do it for 2 years and now she has started again. We have limited water, I have woken her up in the middle if the night, I have tried not changing the sheets. Nothing works. Every night she wets the bed and it has been a year... after 2 years of not doing so!! please help with any suggestions or insights as to why this is happening... I am going broke buying diapers and pull ups! plus she will be 6 soon!