I read not long ago a couple of articles about water vapor in space trapping radiation resulting in star formation. I was wondering if/or when a sun sized star ignited if the outward flow of preasure could cause some of the escaping water vapor to become liquid?

and if so could this liquid water cool down plasma enough to cause it to reform into dust?

Star formation results essentially from gas clouds (primarily hydrogen, not water) condense due to internal gravity. If there is enough matter so that the internal pressure heats up the gas sufficiently (becoming plasma), it will start shining. Water is irrelevant.

I read not long ago a couple of articles about water vapor in space trapping radiation resulting in star formation. I was wondering if/or when a sun sized star ignited if the outward flow of preasure could cause some of the escaping water vapor to become liquid?

and if so could this liquid water cool down plasma enough to cause it to reform into dust?

 

Sure it would become liquid, but only for an instant as it is again frozen solid. It would not have much cooling effect because space is a near vacuum, no convection.