Yeah your post makes sense, which is why she already does this
Onium - Wikipedia
It's not held freefloating in storage cause things in storage move around and is typically not strictly compartmentalised unless a valk dedicates some mental resources to keeping it like that. Anna already uses some mental resources making sure the streams don't cross between her components, so a few milligrams or kilograms of AM floating around possibly bumping into something and reacting would not be a welcome development in there.