Here's an article I wrote: http://erotica-uk.com/top-g-spot-toys/
I recommend the slim-line G-spot vibe by LH for couples play as it has a long shaft and would be easier for someone else to use on a reciever.
The G-spot, there's a lot behind it, and not just the theories. The G-spot is made up of multiple muscles, glands, vien, nerves and more. My favourite way of thinking about the G-spot, is that it's everything working together, and in 'Read my Lips' A book by Debby Herenick, the same way of thinking is ecoed.
There's also debate that some people may not have the same things what a 'normal' g-spot conists of, yet theres still so little research that we can't actually say what is normal or not when it comes to this sweet spot.
Some women don't have the same amount ofd skene glanes, then some nerves in the area are randomly places, then there's a bit part about muscle flexibility.
Flexible PC/ kegel muscles help... this doesn't mean strong, the person needs to have control over them, because not everyone has control over their strength.
The questions you have to ask is why are you looking at G-spot toys when she's doubtful about the g-spot. Part of g-spot toys and play working if that the user / receiver can tell or have some idea about their body and acceptance of the G-spot, which helps them focus on feeling the insertable product and positioning it during play.
But also what will you do if you turn up with a G-spot toy and her beliefs are so solid that she's not even willing to try it. It may be better to buy a different shaped vibe, a clitoral one, or even a couples toy.
Thirdly, during G-spot play when playing with a partner, it better that she feels comfortable beforehand so she can communicate. This is not only important for the emotional side of your relationship, but also be able to tell you when things don't and do feel right. It's so easy to cause bruising in the vagina and general discomfort.