Judging from the drawing, she's around 4-5 times your size..
Since you are 5'11, that means she could be anywhere between 22-30 FEET?!

She's da biggest hun ^-^

Oho.

For some reason this reminds of Hachishaku-sama. It's a Japanese legend, or myth (I don't really know the differencd between the two) and is supposedly a really tall women.
The legend says that she stalks people, preferably small children, and kills them. Apparently you'll die a few days after you see her, so if you don't see her, you don't die... as quick.

There have been some anime shows based off of her, but instead of her killing the small boys she finds, she.. uhh.. 'does' it with them.

Also, it should be obvious, but the anime shows with Hachishaku-sama aren't exactly PG rated. They're 18+. And there isn't any violence in the shows. Sooo...

Also also, the shows aren't shows, they're sort of like a single pilot episode of sorts. I still remember the names of the shows if you're wondering, but a quick google search might help you find them. Well, you might have trouble finding one of them since that one is more well hidden...