Thanks a lot Gray, Jasonred and Kageri for your comments.
I am from China. My Chin is about 500g. I always give my chin pellet and hay of best quality I can find. They are all imported mostly from the US. For pellet, 60% is Oxbow 40% is Mazuri (I did not give all Mazuri because my chin loves Mazuri so much I want to keep her interest by not giving all to her hehe). For hay, I have APD 1st cut, APD 2nd cut, SPS, SPS 3rd cut, oak and wheat grass etc. They all look nice, fresh and smell nice and they are not kept for long time (at least from my side).
My chin used to eat a little bit of hay every day (small handful). Perhaps it is summer, her appetite is not as good as before. For hay I provide constantly and refill every 12 hours. But she now would only touch every other day and eat 1-2g each time. That's why I am worried. When I show her different kind of hay and put in front of her mouth, she makes exagerate emotion she turns her butt to me and run very fast right away to show me how much she hates it. LOL.
If I give her less pellet she would staff herself until the next day the pellet comes. Last night I start trying giving her hay only, she is not happy obviously but she eats about 4-5g. Her health looks okay so far, she is grumpy. She loves chewing, not always to chew toys but my furniture too - sigh. Well, it is better than no chewing though.
I am not sure of the best way to deal with her eating 1-2 g every 2 days. If some says his chin also eat this little and still live a long life (up to average 15-20 years). Then I would be very happy to hear that. Thanks again.