What I think is that she should marry him only if she wants to have sex with him, wash his socks and sit beside him on the couch as he watches yet another boring episode of yet another boring TV show. Because this is what the daily, domestic reality of marriage largely is, when you get right down to it.
I'm not talking about the spiritual stuff, obviously. There are dozens of Catholics happy to tell you all about the spiritual stuff, so go read them if you want to find out about it. I think Christopher West has even developed a kind of Catholic tantra or something, so if you want to mix in some ooh-la-la with your theological reading, off you go to Chris.
Meanwhile, if you are younger than me (it seems) there is also getting pregnant, which involves swollen ankles and having a puffy face and staring down at your huge belly moaning "Come onnnnn, new baby! Hurry uuuuuup!" The new baby will usually look like your husband, so it is important to really like or even love your husband so that you love the fact that his baby looks like him.
Oh yes. Love. I guess I should also talk about love, although now that I live in Britain it is an even more embarrassing word than sex. The problem with love is that we North Americans throw the word around a lot, and tell everyone that we love them. Even North American boys now indulge, as in "I love you, man!" And what you feel when you get a crush on someone can be called love, I suppose, although I prefer the expression "temporary insanity." The British call it "fancying", as in "Do you fancy him?" which sounds suspiciously akin to that other common expression, "Fancy a fish supper?"
For marriage purposes, however, love is not just a feeling of sexual attraction or affection but, in my experience at least, a feeling that you will absolutely die if you cannot marry this person within six to eight months which morphs, after marriage, into the knowledge that life will really, really suck if this person escapes or dies.
Of course, you could argue, that is just me, Auntie Seraphic, over 35 and brimming with natural affections. What of the indecisive young?
I would say that the indecisive young should just sit tight until they meet a person--of proven good character and appropriate family background, beliefs and education--who truly rocks their world. And this is because marriage is not something tremendously exciting in itself, on the domestic level (on the social level it is crucial to the health of society), but a man and a woman living in one space, trying to keep the space and themselves clean, earning money and spending it on boring things, having sex, arguing and watching boring TV. That's what the "marriage lifestyle" looks like, so unless you marry someone who rocks your world, you are going to feel seriously ripped off.
There is a cynical little term that has arisen from people who marry young and soon feel ripped off. It's called "starter marriage." But this is a little term we want to stamp out because divorce should not be an option, and if you're even thinking of divorce as your handy little escape hatch then most definitely you should not be getting married.