I have family members with it and they tend to be much lovelier people than those who look down their nose at them for not having money or high paying jobs and not being as worthy somehow of a "hot chick" as someone who doesn't have Downs.
It's not a whole new level of love being blind; it's your friend having a large heart and ability to love someone for who they are. I'd say you picked that friend wisely and hopefully her influence will rub off on you and others in a positive way.
No, you are right, they aren't stupid and in fact, I'd wager the ones I know are much smarter than a lot of "normal" people I encounter. One particular family member of mine, a cousin close to my age, is probably the kindest person you would ever hope to meet.
He loves people unconditionally, despite the fact that many people have looked at him with disdain throughout his life. I've watched it, that subtle kind of skeeved out look people give the disabled out of the corner of their eyes that they assume the disabled person is too stupid to see.
Despite knowing others view him like this; he will still come up to you, shake your hand and talk your ear off.
I've met others with Down's also and I find knowing them and working to understand them to be very enriching. They have a lot to show us about how we treat one another.
PS Women are not trophies - so "hot" or not; women deserve to love and be loved for who they are and that is in no way dependent on superficial crap.