Can be due to several issues ranging from congenital issues, trauma, microvascular disease, etc. It is most likely congenital since there no suggestion of trauma. Microvascular tend to improve and resolve over months.

Congenital or traumatic nerve palsy that are isolated to just the 4th nerve often engage in prism therapy for several months. Prisms can actually be placed in spectacle lens for many patients. Eye patching is used for some.

If prism therapy is not helpful or indicated, surgery can be considered in many, mostly to correct strabismus. Botox therapy is considered in a few pt. as well.

This is fully in the eye specialist world, most physicians will not be able to give a great opinion about what is best for your daughter. Every case will be very individual. She will likely live a full life with some possible eye deviation concern or visual concerns mildly.

Just my quick two cents. That is about all I know about 4th nerve palsy.