Web Design companies have created websites like yours? Do they have related industry experience? With any service company, if you want to sell products through your website and accept credit card payments, then the web design company thinks you are doing this?
A well-established Website Design company will have a soft portfolio of web sites that they have created for other clients. Ask for a design site link to another site and review each. Do you like what she likes? Is there a style in the sites that appeal to you? Besides reviewing web sites, ask for customer references.