If she has already expressed openness to it then just go for it, but don't go completely for broke at once. I got my wife the 8" all-American vibrating black dildo, she loved it till the vibrator stopped working. Right now she has a 8.5 x 6(albeit white) which looks massive next to me (I'm like 6.5-7 x 5). I imagined my wife taking these big 10 inch dildos but reality is, that size is gargantuan lol. Start 'small' relatively speaking and build up as she gets more experience.