If I create a new iCloud account will it erase my pictures and apps?

My friend sold me her old iphone and it's synced to her new one. If I create a new iCloud will it delete all photos, apps, music, etc? Fine, if that's the case for my phone but my other question is if the same will happen to her phone? She would be so upset if her stuff was erased but I need my own account to activate this phone. Plus, it's getting annoying seeing each others pictures pop up randomly. Any information helps, thank you!

Sign everything out of iCloud then reset the phone. Her stuff won't be affected. Resetting a phone does not delete anything in the cloud or on other gadgets synced to the same account.

She needs to wipe the phone because it will need her password, then you just set it up as your own.