Thanks for the input guys! I know the definitions are controversial, but if anybody has any ways of determining which case we may be facing, please share. The other important question was: how to actually decide when to ease back into high intensity work and how gradually should this be done in order to avoid setbacks?
At the moment my plan is pretty similar to Juthrbog’s: very easy tempo runs and calisthenics types of workouts for a couple of weeks (then maybe a test session of 30 meter accels to see how she responds). She’s using contrast baths a few times per week and massage as needed. Meanwhile I’m asking simple questions like how her sleep quality is, is her appetite improving, is her general mood and state of motivation improving, etc. to keep track of the recovery.