All depends on where you are staying, where you want to see her (and if you have tickets with or without parkhoppers), how you are going to get there, what corral she is in, and how fast she plans to run (with character stops or not). But yes, it can be done.
Here is the course map: http://cdn.instantmagazine.com/upload/2425/wd17_half_course_map.14314adf9f35.pdf
An easy place would probably be the parking lot as they come out of HS. The park has 8am EMH that morning, so you could drive or bus over there, then drive or Uber to Epcot for the finish. If you are staying at one of the Crescent Lake Hotel, you could just roll out of bed to a spot by YC/BC, then book it to the front of Epcot (if you Uber or drive). You may not get to see her actually cross the finish line, but the finish line area is pretty crowded (and I am personally “in the zone” too much by that point to see anyone in the crowd, I am just laser focused on the finish). There will be a long runners only area where she will get snacks, pick up her bag, and get a picture with her medal, so you should be able to get to the family reunion area in plenty of time. Although AK is “midway,” I doubt you could get there with the road closures.
As for end of the race, she will have a shiny new medal, so idk what you could do to top that. Maybe flowers? An idea if you see her on the course is to surprise her by making a special sign.
I have asked here a couple of times if anyone went to the party last year, but no one ever answered! I read reports that there were logistical issues in clearing the park for non-party guests, but if you can last until after midnight, the lines will be minimal.