Thank you for choosing healthcaremagic.
As you mentioned that your daughter has ankle stiffness
and is seeing a physiotherapist for the same.
If her ankle stiffness has been noticed since she started walking and especially if she is unable to walk unassisted, then there is a definite likelihood of her having cerebral palsy
especially since your daughter was born as a premature baby.
There could be other possibilities as well for her dragging her leg especially if it is only one sided and of recent onset which need to be evaluated soon.
I would suggest her to be seen by her pediatrician
or a pediatric orthopedician specialist for her to have a complete evaluation of the same, if this condition is of recent onset, then the doctor might order xrays of her foot based on their evaluation.
I hope this was helpful to you.