Yeah, the g-spot debate is actually a little complicated. The thing that the scientists can't agree on for the most part is terminology- what parts specifically can be called the g-spot. Also the term "g-spot" isn't medically recognized. "Urethral sponge," is generally the accepted medical term. The g-spot itself isn't actually a spot, it's an area anywhere between 1-3 inches or so inside the vagina along the front wall (top). It may be ridged (like the roof of your mouth). It's generally believed that all or most women do have this area inside of their vaginas, but that each woman responds to stimulation of it differently.
My husband and I don't even go near my vagina until nearly half an hour into foreplay. By the time we do, I'm extemely aroused and very well lubricated. It's much easier to find the g-spot if I'm very aroused because it swells. I lay on my back, usually with my upper half propped up on pillows (for no real reason other than it's comfortable and I want to watch. lol). He inserts two fingers and curves them towards the top (front wall) and moves them back and forth, almost like he's saying "come here" with his fingers. I need a lot of repeditive strokes, taps (which drive me crazy) and somewhat firm pressure to come. How long it takes usually depends on how aroused I was to begin with. Some people like to have clitoral stimulation too, but actually I find it distracting. The clitoral orgasm is just so different, that when my husband switches from my vagina to my clit, I almost feel like I have to "start over," or something. Afterwards I'm completely wiped out- walking is so not a good idea! If my husband continues to stimulate me even after and then we have intercourse, I can sometimes orgasm again just from the penetration. (Not always because sometimes I'm just too darn tired.)
That's how I have a g-spot orgasm, which is different for me than a regular vaginal orgasm.
To the original poster- don't give up! It sounds to me like you're doing everything right by exploring and trying out different things. If her mind is too focused on having the orgasm, then it won't happen regardless. Tell her to just enjoy it, and if she doesn't come vaginally, then no worries, you'll work on it again another time. It's vitally important that she feels safe and supported by you, and not pressured. Besides, if what you're doing feels good to her, then you've already succeeded eh? I think the worst thing a person can do is simply write it off like it isn't possible and give up. So please, do continue and by all means have lots of fun!