If I had to guess, when his presidency ends, she will stay married to him but do her own thing. I agree with someone above that waiting for him to die is the easiest option.
She planned on being rich man’s wife, not President of the US’s wife. What she has now involves a whole lot of scrutiny and diplomacy . She probably is sitting in on state dinners which are probably very boring and include small talk, and boring trips where she has to spend time with the wives of the officials while the husbands do their chatting. Instead she could be shopping in NY or LA, or be by the pool, or stuff like that.
I wonder, according to US law, if they got divorced, if she would retain Secret Service protection?