Giant woman as horror only works in an isolated location, like a gothic mansion or deep in the woods.

If you're making Attack of the 50ft Woman in the city then it can only be comedy, a social satire. She has to grow very slowly, and nobody can treat her situation seriously or give her any sympathy or respect. Everybody has to give her shit for it the entire time, acting like they're personally inconvenienced by her situation and it's her own fault somehow.
>6 ft - "Whoa, Becky, did you put on weight?" - "No, my doctor says I'm growing taller." - "Sure, whatever, you just look really bloated. Let me give you some dieting tips."
>7 ft - "Jeez, Becky, why are you wearing those heels? Don't you think that you're tall enough already?"
>8 ft - "What the hell, Becky, why aren't you wearing heels? I know we don't have a formal dress code, but don't you know that there's a bare minimum standard you're expected to meet?"
>10 ft - "Holy shit, Becky, did you just break that chair??" - "I'm sorry, I--" - "Don't worry about it, I'll handle it, you just go back to your desk before Stacey gets here." (later) "Oh my God, Stacey, you'll never believe what Becky just did!"
>15 ft - "Go home, Becky, just... that's enough, go home. I'm sorry about your health issues, but you can't come to work if you can't even fit through the door, so you need to take some personal time until you can get your weight problem under control."
When she finally gets big enough to destroy buildings, it's a humorous comeuppance for all the assholes who deserve to be put in their place.

Scale for most of the movie:
https://www.youtube.com/watch?v=AYmqqelYJa4

Opening credits song:
https://www.youtube.com/watch?v=agrXgrAgQ0U

Closing credits song:
https://www.youtube.com/watch?v=zRZpaxBMJRU