How would you distinguish in French "She has doubts about her husband", as here, and "She doubts her husband" (i.e. she does not believe her husband)?
I would say "sur" is what makes the difference here.
Elle a des doutes sur son mari.
Elle doute son mari.
I'm assuming that the noun "doubt" is the same as the verb "to doubt".
why does the sentence take "sur" with "avoir doute", but "de" with just "douter"?
I tried "Elle a des doutes à propos de son mari." and it was accepted. Quelle surprise !
Hmmm... gotta trust a woman's intuition!
Isn't "elle s'en doute de son mari" also possible?
No. Elle doute de son mari. Elle en doute.
What do we think of “Elle a des doutes concernant son mari,” which was rejected?
Not a native French speaker but this was my first thought but given Duo's (random) literal approach, I did a check here http://www.wordreference.com/enfr/doubts%20about
Switched to "Elle a des doutes sur son mari." which was accepted
The french and english sentences are not saying the same thing.