Tell her that you understand she wants her relationships to be equal, but that she probably wasn't going that fast with her husband when they had been together four months.
And even if she did, each relationship is different, and treating people differently doesn't mean you're not treating them as equals.
Can you just send this post to her in an email, or read it to her as you are talking? It seems to me you explain the situation well in it. It could be a starting point.