I hate how Western women who are supposed to be well-educated (compared to many women in the Arab world) get brainwashed and convert to Islam and help breed ignorance (Islam honors women, etc)
If you asked her if she thought it was OK for young girls to be married to adult men, middle aged or old men, she would of course say that such an idea is repulsive to her.
If you said to her that such things happen in some places in part because it is deemed to be 'acceptable' because Muhammad did it, she's in a tight corner. Because if you accept Islam and start to revere Muhammad you have to accept his sunnah in every respect. Because if you reject or criticise it you're rejecting and criticising the Prophet and that is blasphemous.
So I guess the response then is to deny it, or to claim that pointing this out is Islamophobic, or just to stick your head in the sand.
But it shows how if you are a westerner who converts to Islam, you really have to tie yourself in lots of awkward knots to square basic liberal ethics with aspects of the sunnah and Islam as practised by much of the schools of Islam.