Brake pedal half way to floor before stopping

[Metal Wing]

Hey guys, I'm posting this on behalf of a friend who drives Mazda 3 2006 2.0L.

Here's her story:

"I went over a pot hole and started noticing the brake pedal was going half way to floor before stopping. I took it to a mechanic and had the brakes bled and Brake Master Cylinder replaced with no change. After I took it to a Mazda service center and was told the ABS Hydraulic Unit was not holding pressure and to replaced the hydraulic unit program and bleed system. I was quoted $1600 for the replacement and I am not sure if this is actually the root cause. Does anyone have any other ideas?"

The reason I am posting this here is in hopes that this may sound familiar to someone and they know of a fix. And if not, perhaps you guys can recommend a good service place in Mississauga (ish) area, that perhaps specializes in brakes (if that's even a thing...). Or just comment on whether the quote above sounds reasonable.

So yeah, any help is appreciated!