it does not feel like godmodding no. But it is a very powerful character.

we'd suggest something along the lines of what others above have suggested:
1. She can't be "killed" in a way that prevents her from ever coming back
2. If she is killed, her soul is returned to hell, where she gains a new body.
3. Once she has a new body, she will have to work her way back to earth.

additionally, we'd suggest bringing in features like her body being vulnerable to the things demons traditionally are vulnerable to (blessed things, holy water, etc.), but because of her nature as a "higher" demon, it merely banishes her as described above, rather than obliterating.

[hr]

Some players don't like having really powerful characters in their RPs. Sometimes they show that by trying to force death on the character, rather than simply saying no to the character before it is in the story. 

It probably wouldn't hurt to make a few notes on the character sheet about how the character is very powerful and that you know that and you do not intend to abuse this trait. If you've got that in there, other players will know about it if they read the sheet.