Thats crap. Sure it is a new experience & most kids probably do take that few weeks to settle in. BUT She took your DD & dunked her in with out letting her be comfy first. No way is DD going to go along next time & think, "OH I remember this, it was great fun"
I would post pone the lessons for a few months & just keep up with your own water play together.
You need to reintroduce her slowly at her own pace.

IMO professional Swimming lessons so young have no real benefit. You can build water confidence & safety through your own common sense & you can do it at a pace that suits both you & your child that way.