can a Task report (or assignments filter) group by project and "sum" of projects?

simplest: is it maybe just a project report filtering on every project where she was on the project team? (i.e. when you're assigned a task you're automatically assigned to the project team) This is also shown as a "projects I'm on" filter in Workfront Classic.

little more complicated: again, a project report with a collections filter for tasks or assignments where user id = your user's GUID? It's very similar to this one: https://wf-pro.com/textmode/text-mode-filters-exists-notexists/#projects-with-active-assignments-to-me but instead of active, you want to do all, and instead of "me" you want to do your user.

Either way the only way to get a sum total would be through the summary tab, so you have to choose a grouping (I would probably group by the user's name, because this would give you the smallest grouping)