Board Thread:Naruto Discussions/@comment-46973520-20200924153856/@comment-39350828-20200925221129

or she ate the fruit and then surprise attacked isshiki because she knew her betrayal would mean she had to fight him. Also, there's not really any reason not to eat the fruit first and then attack isshiki as opposed to attacking isshiki first and then eating the fruit. It's also hinted that having the ten tails gave kaguya the rinne sharingan which she had when she betrayed isshiki.