If she was aware that he was planning something or assisted in any way to help him prepare, then yes, she is guilty of conspiracy to commit murder. I haven't heard evidence that she knew anything so, until more is known, can't answer yes or no.
"Aware." "Something." "Planning." These are inherently vague. For example...
Mateen: One day, I'm going to give those fags what they deserve. I'm serious. I'm going to do it.
Saying this to his wife means that the wife was "aware" that he was "planning" "something."