She can easily read words like beautiful when they are presented in context but struggles with simple words like why, that, etc.
This was my DS9 exactly - the big, complicated words were easy for him, but he would confuse the simple words, like he'd confuse "was" with "saw." This was very strange for me since DD11 was a phonetic reader from very early on (she always was and still is a reading ace), so for me to watch DS read by memorizing words rather than by sounding them out was very odd.
Fyi I didn't really do anything to remedy the situation with DS... he was already a bit ahead of his peers (like, at a KG level when he was 3), so I let it be. Now the situation has taken care of itself - not only is he a phonetic reader now, but his fluency has increased dramatically.