HI and welcome. Glad you started your own thread. I agree with all of the other responses. It sounds like as a preemie, she likely has residual effects because as you well know, there are things associated with the early birth as well as the treatments to keep them going and developing once born. The sensory issues, language issues, motor issues seem to have gone on beyond the usual adjustment times and the attention issues plus sensory issues often are associated with other things so while very real individually, they may go under a bigger developmental umbrella.
If it was me (and I didn't have a preemie but do have a medically involved youngster) I would for sure get a neuropsychologist evaluation (and I did, several times). I agree a really good Occupational Therapist (OT) evaluation would be also super helpful. Sounds like she has texture and sound sensitivities so when you call ask for a sensory integration evaluation as well as checking her fine motor skills.
How does she do socially? Does she play WITH friends or along side of them, running, chasing, using the same toys.... or does she need to be guided in her play? Can she create new imaginative ideas with toys (like using a rock for a pet and a pen for a person or she herself can be another character....but not just saying what she heard other kids or a tv or movie say)? How does she do going from one activity to another? Her sleep issues are also a concern of course. So, once she does settle with you does she stay asleep?
You must be exhausted with all of her energy, smile! but she sounds delightful and it is wonderful that the medications are working. My son has general umbrella diagnosis that includes adhd symptoms and medications help him too. We use Ritalin (concerta, the long acting form).
Nice to get to know you! Welcome to the group.
