This is my opinion.
She was also injured at Boise State for a while so her injury issues have been dogging her for a while now.
If you look at her family's general body type (Teri and Paul I think are her parents), they don't look like runners from a physique standpoint. Allie's genetics gave her God-given talent but at the same time wanted her to be naturally bigger as an adult. Nothing wrong with that, we're all different sizes based on our genetics. These are two opposing factors that is not sustainable for elite running. She has been fighting her body and maybe she is not meant to be a runner even though she has the talent. Maybe she is meant to be a world class XC skier but just never realized it. Skiers tend to have a higher muscle % than elite runners and high VO2max.
My point is she is right to pick things that are better suited for her body than trying to compete against sticks from East Africa. It's not fair for her or her body to expect that much. This is a problem for many Western-born women. They just can't keep up, body-wise, with hyper efficient skinny women form Kenya. That's not what European genes want...especially if you have nordic ancestory.
With that said, if Allie wants to give another go at this later. Maybe that desire comes back. She can talk to Nell Rojas. Nell is a chick who is naturally a bigger, muscular lady but makes it work by a ton of strength training and such.