I personally have not dealt with Zhili-dresses.com, but you're right, their dresses look amazing. Their website was registered in 2001, and that's good because that means they're pretty much established. However, I did not find a lot of information on their website. For instance, their accepted payment methods. You should always use a credit card to purchase goods. This form of payment is safe because it gives you a comeback if something goes wrong. With this payment method, you can usually have the transaction reversed fairly easily if necessary. My other reservation is their contact email. Both their email addresses are hosted on free accounts, of course, this is not a guaranteed way of telling whether a supplier is good or bad, but suppliers whose contact email address are at their own domain name are more likely to be legitimate.
If you would like to use them as a supplier, I suggest you contact them directly and ask as many questions about their products and policies as you can before you go any further. And if possible, call the supplier's telephone numbers to ensure they are genuine. You can also purchase a sample before bulk ordering to ensure that the item meets your expectations and at the same time test their speed and service.