I will not be a hypocrite here and tell you it's none of her business.
It used to (still would, if I knew about it) piss me off when my W would leave my kids alone for a night, or if she got FIL or other to look after them, or if she just shipped them out to visit their friends so she could go out...
Still, your 16yr old is of an age that it is acceptable to leave them for a night. The only thing that would be important would be that an adult is available to them in case necessary.
Tough call. Did you HAVE TO tell your W? No. Would it have been respectful to tell her? Yes. Would it have been respectful to give her first option to have kids while you were gone? Yes.
But it was not necessary... Her feeling of offense like mine, is hers to own...
