"Are you still married to Mary?" How to translate this?
I can see you've tried at least one or two things, and it's a tricky question so I'll give it a shot.  Remember, courtesy is everything in a forum like this one.

The problem is that 'to be married' is an adjectival form in English, and there is no corresponding adjectival form in Chinese. That means you can't get a word for word translation. Instead, you will have to rephrase the sentence, perhaps drastically, in order to get the information you want,  

Rephrasing takes practice. It's not always easy to find other ways to say what you want to. One way to do this is to treat the process as an English exercise. Look up all the words in a regular bi-lingual dictionary.  

For example, in the Oxford Advanced Learner's English Chinese Dictionary, I look up married. The definition gives 結婚的, 己婚的, then lists phrases that use this sense:

a married man   己婚男子
a married woman 己婚女子
a married couple 一對夫婦

The last one is the solution you want, since your sentence can be rephrased in just this way:

Are you and Mary still a married couple?
你跟瑪麗兩個人還是夫婦嗎?

Not 100% the same syntactically as 'Are you still married to Mary', but the sense is almost identical I think. Asking this in Chinese I'm sure will get the information you want, without any strange semantic or social mismatches.