It makes sense. Ella gets ecstatic when MC tells her about the ability to copy other lifeforms and she call him perfect. I thought about it too but I actually don't think that it's what Ella wanted. Or to be more precise, I don't think that she wanted the memory to copy other powers.
One thing I've noticed about Ella's transformations is that they are very abstract. When MC transforms into a dog, he creates a perfect dog. Her wolf was a bit eldritch. I think she wanted the memory in order to transform herself into a very specific thing. Perhaps a vat for power.
Ella knows things that others do not. Like for example that the 5th evolution isn't necessarily the last. It's just a very important milestone. Check out this conversation. It happens right after Ella heals Mia:
It's quite possible that she thinks she can't do what is asked of her because she can't transform into the exact thing that her parent wants her to and instead of wasting her time, she decides that Eli has a better chance of succeeding, thus she immediately turns her over to the Fourth. (Which begs the question, why the Fourth and not the Third, since he is her monster father? Which could be answered by the notion that Third and Fourth like each other and work together).
This seems quite a huge "spoiler" for the HERO boys and something that seemingly no one knows in the organization, despite having so many level 5s. It's also one reason why I think Nyx is going to do something awesome that no one expects her to do.