Spoiler: I am sure we have not seen the diary, she did not recognize the diary specifically and did not even recognize what it was written in it, but she did recognize the way her name was written, she said 'This is the way I write my name' (my translation of her words from Korean when she was with KiChul), so diary is a matter to pop up in the future. Also in the 10th episode it's official, this is not the first time she's there... He has been there last time too, she has saved the Queen, witnessed the child king's death, saved the young man she saved in 10th episode who is then going to exile ChoiYoung... she's still moving according to the history she knows and is now afraid to change anything in it...
I am just wondering how she is going to manage to transport to the future and then back time still before Goreo and again to Goreo... she has to have the diary (from future), in Goreo it must be at least 500 years old... innnnteresting... drama, don't disappoint~!!! end of spoiler :p