“Disobey Stop Sign With Collision”

Hi guys, I would like some advice.

A family member was involved in an accident two months ago. She didn't stop at a stop sign in a 50km/h zone and hit the right side (passenger side) of another vehicle going perpendicular to her. No apparent injuries to anyone. When police arrived, she admitted that she did not stop at the stop sign and was given a summons for disobeying the stop sign (collision involved).

This was the first stop sign after a row of three traffic lights (no sign indicating stop sign ahead, although there was one after this intersection ). She did not notice the stop sign before the collision, and upon later inspection, she noticed that there was a stop sign on both left and right side of the road. The road was in an industrial area with two lanes in each directions. The right-side stop sign was obscured at a distance by a bus shelter. The left-side stop sign is not obscured, but basically four lanes over as she was travelling on the far right lane.

So I was wondering how she should proceed at this point. The main concern is the rise in insurance premium. There is already the at-fault accident, but being charged would hike it up more. She had been a stellar driver with no tickets of any kind until this.

1) Should she plead not guilty or is there not enough of a case to make? As I understand, there would be several options laid out at the summons: plead guilty (pay fine), not guilty (set trial date), and maybe plea deal (pay lower fine).

2) She did admit not stopping at the sign to the police, so would that be considered guilty no matter the circumstance?

3) The summons is next week, and she doesn't want to miss a whole/partial day of work for this. If I or another family member go in her place as a representative, should we have a signed form from her?

4) Does having a collision involved impact the fine? I researched online and the set fines for "Disobey railway crossing signal — fail to stop 163(1)" was $85.00, so I'm guessing around $100 with court fees and other fees.

Any input is appreciated, thanks.