I have noticed it helps when the person uses there phone. I know whenever I load the browser it locates me. when It does that it updates my latitude for my gf.
Not sure what phones your gf and "other friend" have but my fiance, my dad, and my brother who have either android phones or a blackberry theirs is updated on constantly, only true updates however come when someone moves from their location, so it may say that it was last refreshed 10 hours ago due to the fact that they havent moved, i know windows mobile phones you had to actually open the app and iphones well yeah they only work as well when you open the app, unlike the android and blackberry phones that always have it running in the background.
This is completely untrue. I've seen my friends leave work and I know they are enroute home (like a 40 minnute drive) and Latitude will still showt hem where they were 10+ minutes ago.
When my wife and I both had blackberries Latitude updates were constant. I could drive down the road and my wife could watch and would know exactly where I was. Not the same on our Droids for some reason.
It's one of the very few things I noticed the blackberry did better.
