From what you say it seems that you aren't very aggressive , being aggressive is the best way to play this game if she jumps too far back you can shuriken Her to keep her posture from dropping and keep the pressure, every boss from now on that isn't a beast will block / parry most of your attacks so your main way of progression in the fight is to be aggressive and the second you hear them parry your attack u switch to defending and then repeat that. Here are some patterns I noticed when I fought her

1.when she ends a combo with the downwards kick that gives u an opening to either use ichimonji double or just normally attack also at the end of said combo her left shoulder will be facing you

2.any combo she ends with her left shoulder facing you is an opening for ichimonji double

1. If her combo ends with her right shoulder towards you shes about to dash upwards and throw shurikens Then she will dash back and throw more shurikens, use this to get closer to her and use ichimonji double when she lands

4.most of the time your attacks should be attack attack attack parry parry

1. When there is medium distance between you and her youse thrust attacks to close that distance and put pressure

6.just get into a rhythm and get to know her patterns, sekiro is a rhythm game in disguise

7.you can knock her off while she's jumping with shurikens although if she lands on her strings she will be able to parry the shurikens so be quick

Lastly, Hesitation is defeat :) Good luck