You can garantee that any quote provided by and designer be it interior or anything else will be inflated. It covers the project management time. If she gives you an itemised quote it will still be inflated. You can't expect people to ring around, get quotes and source materials for nothing. Yes they say no worries I will do it for you, but ask yourself why? Is it because they think you are a fantastic person and really just want to help out :no:or is it a means of them making some extra money:)?
I agree with Mr Fix It, you can not expect the electrician to deal with you if they have an ongoing relationship with the ID. Get other quotes as suggested. If money is not an issue and you want someone else to deal with any headaches, go with the ID.