I'm a big AllieO fan, so take everything with a grain of salt...
I think her best chance in 2020 is 10K, and best chance in 2024 is the marathon. When I first saw her running a few years back, as a senior in HS, I thought "this is Joan Benoit Samuelson reincarnated" - but of course Joan is still with us...!
Allie has a great marathoners' efficient stride, and seems to excel at longer runs. I've heard she will focus on 10K during spring 2019. If that is accurate (and it might not be true), then we will learn a lot more about her ability at longer distances. Corey is a very solid distance coach - so I think we will see a good picture of Allie this spring in the 10K without a huge amount of "professional-quality" work. My guess is that if AllieO is top 3 this NCAA outdoors in 10K, then she has a great chance of making the 2020 10K olympic squad. She's a keeper.