Do attacks granted by accelerated assault (aa) or hypersonic assault (ha) count as having made those actions for the purposes of triggering unrelenting momentum (um)? So could she sprint(1st action), nimble strike(aa), sprint(2nd action), nimblestrike(aa) nimblestrike (um), sprint (um) sucker punch (aa), sprint (3rd action) sucker punch (aa) sucker punch (um) to attack 6 times in a round?
Unrelenting momentum is only interested in the actual actions you take. If what you did did not cost an action it doesn't count.
2 Hypersonic Assault uses will trigger a free Hypersonic Assault via UM.
2 Sprints will trigger UM and grant you a free sprint, the attacks each of those actions lead to (using Accelerated Assault in the case of sprinting) do not use actions and so they do not cause any interaction with Unrelenting Momentum.
The course would be
Sprint (Assault), Sprint (Assault) 2 sprints trigger Unrelenting momentum granting a free Sprint (Assault)