ok so def get a realistic thick dildo for her, pref silicone. use this when youre together and more and more talk about it being a different guy. who stays hard all the time and can go all night.
also get her the hitachi wand as its amazing ability to make her cum will make your fingering her useless.
also next time youre close to cumming ask if you can, basically give her control if you can cum or not which will get her thinking of denying you orgasm, which will make her more and more dominant and knowing she can control things (and later will be able to reamister she can fuck any guy she wants)
and saved some big dick pics or gifs for her. ask her if she thinks she could ever handle a guy that big