honestly? find a store that has both, and give her a card that says you two are going out to have a special holiday, take her to brunch, and then take her bike shopping. or, get an old beater bike at a garage sale or goodwill, put a bow on it, give it to her, and then say, "but the real bike is still at the bike shop."
this because the specs, components, etc. are not the issue at that level - it's the subtlety of personal preference and fit. she has to ride them before she knows which one fits her best.
when i went out bike shopping, i rode probably fifteen equally nice bikes from different companies.. similar components, etc. one emerged as the clear winner, just because it felt right. i'd bet that the same will happen for her - or she may even find out that neither of those is perfect, and she'd like to ride a few more. either way, that's quite an investment, she should get what's perfect for her. (imho).