Some females hate tounges, some females only cum with their mans tounge down there.
Some can only cum with dicks, and some can only cum with vibrators.
If you ask me, it has to do with how crazy your female is.
Orgasms... mmm. Probably only happens to a female when she is completely mentaly stable(thoughts completely clear).
If shes a crazy bitch shes never gonna stop thinking so shes never gonna cum.
I'd say if you wanna get your girl to cum really really hard you gotta find a way to help her mind stop thinking so negatively.
Try to do some meditation with her, get her to think super positive about herself, and try to get everything in her life on check(if your really good teach her the same thing so she can help you out with your life).
Im not a female, so I can't tell you exaclty how they feel. But im pretty sure that some of them just see oral sex as nasty, and some see regular intercourse as not good enough. You gotta work with her bro, find out how shes thinking.