It would almost certainly be perceived as insulting. Though, I suppose that often is the entire point of giving a politician a nickname.
Alternatively, there's the classic 'Iron Lady', which first took off with Margaret Thatcher but has since been co-opted for all powerful women operating in otherwise male-dominated industries.
Another option would be to go with a poisonous flower motif such as 'Belladonna' since such flowers are often beautiful yet dangerous.
Overall, the cleverest thing for you to do is to try incorporating part of the character's back story into the nickname. For instance, if she or her family was involved in construction, using the word 'stone' as part of the nickname would be especially fitting.
Hope that helps.
Just had a thought... what are your thoughts about the 'Duchess of Masks'?
edited 4th Dec '12 5:22:01 PM by peasant