Orgasms have fascinated me for a long time and i have studied every article about them that I can find and have tried most techniques mentioned mainly with success, so I consider myself rather skilled. One lover I spent the night with taught me that I still have much to learn, I showed her all my moves that got previous lovers into higher states of ecstacy, but no matter what I tried, no orgasm.
So I researched more and discovered that some women just aren't wired up the same. It is possible that they have fewer nerve endings around and inside the vagina, there could be a hormonal problem, testosterone is important for orgasms, low levels can reduce the chances of coming.
The most important erogenous zone - the mind could also be a major reason, medication or psychological issues can block the final build up to orgasm.
I often wonder if some women hold back because they are squirters, the bladder pressure at the point of orgasm is so uncomfortable that it discourages them to let go and let the orgasm with female ejaculation happen. (Can anyone confirm this?)
That girl still managed to have and give lots of pleasure so I don't think it is a real problem.