Does the IOS7 download affect any apps?

No it depends on how many apps have.

My sister got it and all the apps look cartoon like and not nice. Really the update is ugly.

I am not getting it. Though,from the last update I got I लॉस्ट all my apps ,because आप need a lot of storage अंतरिक्ष for it.

In rare cases,it tells आप that आप need to मिटाइए so much data ,but not always.

If आप have lots of apps and like it how it is I wouldn't risk it.

Anyway if आप are unsure about how it looks ,then this how it looks.