There are many ways to do it and I’m not an expert on that. One way could be asking her what her main goal is for the site. Is it to get the user onto an email list, buy things from the site, or to increase the traffic in her salon. The website can do multiple things but having a main focus can help you figure out the required content. She might even have an idea what she already wants so you could ask her what her dream website has/does.
On a last note, make sure you have a contract that details what is expected from each of you and what is included. For example, will you offer maintenance later on? How much is your charge per hour, or maybe she wants everything taken care of for her regularly. Will you have a monthly cost? Do some research and do your best. Let her know if there is something you can’t do by offering an alternative (instead of saying no). If you for sure won’t be able to do something she needs, tell her the truth.