Congratulations!
Since you'll be traveling with a casual friend, determine in advance:
If you're both morning or night people. Or not.
Touring style. Do you both like to be on the go or be more relaxed?
As a PP mentioned, food preferences.
Budget, and how expenses will be shared/paid.
What really interests her about visiting WDW.
That covers the basics.
What about giving her one of the gentler planning guides? Something with substance, but not so much information it will overwhelm her.
Many of my WDW visits are with my BFF (California resident), and our touring styles are very different. So are our food preferences, although hers have become a bit less spicy and I'm a tad more open to experimenting-occasionally--than I used to be! *LOL* We've been best friends all of our lives, so we covered costs and internal schedules many years ago.
When we visited WDW in 2003, it was her first visit, and my first visit in 22 years!

She did not want to plan at all, but I joined The Dis and a couple of other sites and quickly learned that at least a little planning was necessary. We didn't follow the plan exactly--the weather had a bit to say about that one day!, but we did all of the things we really wanted to do. She hasn't wanted to plan at all for subsequent visits, but I put my foot down on a few things, and she goes along with it. We wing a lot of our WDW holiday time, but we visit for 10 to 12 nights each trip and have a little extra time to relax.
You already know that some planning is essential. So at least check park hours and events on the days of your visit, and keep the information with you so you can share it. Tell her about ADRs if she is interested in TS dining and let her know that it may not be possible to walk into a restaurant or even make reservations after you arrive. Plan attractions both of you will enjoy, with some in her favour, others in yours.
My BFF loves to shop, and I barely tolerate it. She can be lost in a gift shop for hours, so I'll go outside and wander a bit, look at other things, chat with other people, etc. She is respectful of some of my physical limitations. We just use common courtesy, and sometimes split up for several hours, or even a day. It depends.
There are so many variables to factor into a WDW visit, besides the parks and resorts. The weather, each person's physical condition, interests. If one person doesn't mind being drenched, but the other worries about hair and make-up, that has to be considered.
You get the idea. Figure out the common denominator and work from there!
And have a fabulous WDW holiday!