I never thought of Ayu as "too westernised". She certainly likes the US and the English language but I don't see that as defining her as "western" or "anti-Japanese" or anything of the sort.
To me, Ayu's constant hair style changes and her music ARE her. If she was to suddenly drop the Roman lettering in her titles and use Japanese, or if she decided to leave her hair natural and never change the colour again, she wouldn't be "the" Ayu anymore. Fashion icons can't go around wearing the same thing forever and musicians can't progress without experimenting with different music styles or wording.
If Ayu were to change all of her song titles back to Japanese, stop using English words in her songs and leave her hair dead straight and brown for all eternity, she would become to me just an average J-Pop singer. Nothing about her would stand out and she would be lost in a sea of thousands of other wannabes and try-hards.
A huge part of Ayu that I love is her willingness to try new styles, to put herself out there into the public with something that could be seen as scary and slowly let people appreciate it. Her hair styles haven't always been great but you have to admire her for trying them. Also, in my experience, Ayu is one of the first Japanese singers I've found to use English letters for every single one of her songs. Lots dabble in English and lots have 2-3 songs with English in the title but Ayu is the first I found to use it every time. This might be seen as very bold in Japan (it is to me) and is one of the ways Ayu pushes musical boundaries (it's a shame this style isn't appreciated and reflected better in our musical charts!!).
But putting that aside, Ayu works very hard, why can't she enjoy her little free time to change her hair style, to experiment with different sounds, to dabble in foreign languages here and there? I certainly would if I had the time