There may be a couple of ways to do this, but I think the the easiest is to ensure your daughter has a different (higher) level of access as a user than the other two. So if all three are currently “members”, increase your daughter to “editor”. If all are editors, make your daughter “moderator”. I would expect that as she is your daughter that should not be too great a problem.
Now create a new gallery just for the pictures of your daughter, and set it’s access level to the same as she now has. You will need to place those pictures in their own sub-folder as well.
To do any more than this would mean allowing a module to have access control by user, which is not very practical.