I'm so sorry to hear about your daughter.
If you find your local MAW chapter's website, they will have all the information you need about getting her referred. If you don't know which chapter is local to you (some states share a chapter, some larger states have multiple chapters) MAW America's website has a zip code locator. There are four people who can recommend a child - a parent, the doctor, a social worker, or the child themselves. You should have no problem doing this as a parent, and they will walk you through the rest. The referral form is right on the website.
As mentioned above, make sure to look for ideas for wishes! A really good resource is the MAW websites themselves. They usually list their past wishes so you can look at what other kids wished for. When MAW volunteers come to your house to help the wish kid figure out what they want, they sometimes play the "wish game" which you can play yourself. All wishes usually fall into four categories: I wish to go, I wish to be, I wish to meet, and I wish to have. The wish game asks the kid "If you could go to any three places, where would you want to go? If you could be three different things/professions, what would they be, etc." Then they trim it down from there. Ex: "You said you would want to go to Disney World, Hawaii, and to Paris. If you could only pick one of those, what would it be?" Eventually, as the kid eliminates things they don't care that much about and start talking about what they are really passionate about, you get a good picture of what they want.