My FDW has asked for Wifi password. I am not comfortable giving it as she is already on the phone all day long - I work full time, so hard to limit phone time). She has internet through her phone. What do you all do?

I read there's a way to limit usage by reassigning a sub IP address to her. My friend did that and I thought that's a good idea to reward the faith in her. However, she already uses the phone whole day. I'd think constantly chat with her to suss out what are her reasons to be on the internet whole day, before giving her wifi access.