Legal advice needed (Alberta Canada)?

Earlier today my mom was at Costco with my brother, and as she was backing out slowly she is suddenly hit by another car. She has a 2015 Ford Edge so it has censors for when she is backing up near something, and apparently they didn't go off until the last second.
A woman comes up to my brother's window, he rolls down the window and this woman begins to yell and swear saying "Why did you hit my f**king car?!" and so on.
My mother yells back to her that it isn't her fault (Which I don't think was the right thing to do in the moment, but it happened). While my mom is calling the police, my brother went out, got pictures of the dent on her car, and their license plate. It looked like both cars had been backing up at the same time, but we assume they had backed up suddenly (Explains why the censors didn't go off.) The husband of this woman comes out of the car apologizing to my brother and mom.
While my mom is talking to the person over 911, this woman gets in her car and drives away.
Later a constable calls and asks for information. He is no interested in anything besides my mom filling out a police report, and that charges can only be made if they do not fill out a police report within 7 days because it was in a parking lot. No insurance information was exchanged or anything.

Added (1). Later my mom and brother spotted them at another parking lot and took some pictures (Which again I admit was perhaps wrong on their part) but then this woman screams and swears again, calling them stalkers. My mom yells back again, but it's short lived and they leave.

Added (2). So now we have a problem. My mom has a dent on the back of her car that is probably going to cost thousands to fix, when she claims it wasn't her fault. Technically I can't say anything was right or not because I wasn't there, so we don't know what to do. The constable wasn't concerned with anything and this doesn't feel right.
Thanks for reading through all of that, I really need some advice.

You have Costco in Canada? That's awesome!