How do I get into my deceased daughter's iphone that I am paying for?

I am sorry for your loss. You can’t get into the phone unless you know her screen unlock passcode. You can request access to her Apple account, which will give you the ability to reset the phone to factory settings and also give you access to her backup and anything she synced to iCloud. The instructions to do that are in the Related Article link at the top of this page. But there is no way to access the actual contents of her phone.

You follow the instructions on the page you just came from.