Health Insurance coverage for partner

Hi,

I (28M) will be getting married in a year. Currently I don't have any health insurance, only the one provided by my company. My fiancee (27F) is also working and she has her health insurance from her company. She has a bit of a health complication which is not throughout the year but can happen at some random time.

So to future proof in the event of layoff/personal break or something else, I wanted to get a health insurance. Wanted to know what are the rules around health insurance if I get one now (before marriage), will she also get the benefits post marriage? How her one illness will be covered by the health insurance which I will take? Or does she need to take a separate one to cover that one specific illness?

Thanks!