This profile is open so you can change the dates and add sources, etc. without being on the Trusted List. Since you are her daughter, you might want to contact the Profile Manager, explain your relationship and ask to be on the Trusted List or ask if you could be given her profile as Manager.
At the very least, you can now go to her profile and change her death date - be sure to post a source.
All of this depends on your membership - like Dennis said - at least a Family Member or just go ahead and become a full WikiTree member.