Ask her if she can do any better.

"Can't you go any faster?", you ask Doe.

Her hands starts moving just slight faster and she stops look at your face and focuses intently on her hand stroking your cock.

"I mean it, squeeze harder and go faster", you add while thouroughly enjoying your handjob.

Doe makes as hard a fist as she can and continues to pound your cock.

"Come on faster!", you grunt down at her.

"I'm going as fast as I can John", she replies nervously, shile moving her wrist so fast she fears losing control of your pulsing shaft.