I really like the fact that the story is a litlle bit strainght forward. She is really really quickly at the stage of goddeshood, which I think is nice. 

Very good story, hope you will continue ! 

I love a good ascension story! This was really great for a one shot. You're quite skilled. The power use with her controlling all the people on Earth waas great. I can totally see someone like Ivy doing that and thinking its just the best thing since sliced bread. Also liked her at the interstellar/galactic scale. Don't think I've ever read a giant goddess smashing a galaxy with her tits. Too bad for Cindy snoozing on using the serum on herself instead. It does kind of lose some of its magic when she's large enough that she's eating galaxies, which is a risk inherent in any story where the giantess grows so large that its hard to interact with anything.

Maybe you could do something similar but starting out smaller and the powers/size growing over several chapters/ the length of the story. Add some secondary characters for the growing woman to interact with and possibly show her changes from an aquaintance, friend or significant other's perspective or alternate between perspectives. Or even from random citizens perspectives when she becomes to large to hide or chooses to make herself known. You could even have friendly or adversarial relationships between more than one giantess.

Again, great story. Hope this helps you make something even greater!