What illuminates the grave despite the presence of two lamps?

The best thing you can do for your friend is to supplicate for her that Allah illuminates her grave, for the Messenger of Allah, peace and blessings be upon him, supplicated for Abu Salamah when he passed away, saying: "And make his grave spacious for him, and illuminate it for him." In some narrations of the funeral prayer, it is narrated: "O Allah, illuminate his grave for him." If Allah answers your supplication, He will illuminate her grave by His permission.