From the movie "Proteus" (fairly lame sci-fi movie from 1995)
Creature enters and liquefies it's victims absorbing them into itself and takes their form. This movie has two brief female melting scenes. First one begins here
second one is very short and doesn't show much
There's also a short poorly done female to monster TF in those few seconds, and a short poor quality male to female TG shortly before. I say poorly done and low quality because like so many bad movies they relied on cheap computer morphing effects.
Also I apologize for only being able to find a Spanish language dub.