I'm new here and haven't formally introduced myself yet, but had to post my best wishes to your DD.
I recently had to go to the local breast unit, with a dimple in one breast. It was an un-nerving time, hubby was quietly frantic with worry but the unit were superb. In two hours I had mammogram, ultrasound and biopsy. The staff were cheery and kind and the consultant was attentive. I came out with a dressing on my breast and the warning I would probably get some painful bruising over the next few days (I didn't have any at all in the end) and I had to wait two weeks for the result, which was negative. If it had been something 'nasty' they would have called me in sooner, but I was one of the lucky ones. Yes there was a small mass there, but it was nothing to worry about and it was probably age-related. I return in 6 months for a check up.
So I really hope it goes well for your DD, try not to worry too much both of you, though it's easier said.