Our ballet teacher has our girls do heel raises with a tennis ball between their ankles...making sure they are rolling up from their heels to their toes slowly.
(resistance) You could have her sit down in a pike & point her foot as hard as she can against your hand while you're also pushing against her foot...hold that push for about 20 seconds then let her relax...repeat
Calf raises with toes turned in and then out (as well as regular calf raises). Jumping side to side (feet together) back and forth over a line/velcro strip.
One exercise given to me by a physical therapist during my dancing days was to stand in parallel, releve, with my ankles together, and then (while staying on tip toes) rock slowly from side to side. This works all the little muscles on the sides of the ankle that sometime get forgotten.