Both. To say she has a limp tells us that whenever she walks, she will of necessity limp. She has a condition that, at least at the present time, forces her to limp.
To say she's limping simply observes that, as she walks now in my view, she is limping, for whatever reason. She may have a pebble in her shoe, or is simply affecting a limp for whatever reason. She does not necessarily have a lasting affliction.
Student or Learner