No need maths so much. If car has to brake for moto entering, it wasn't safe for moto to enter the lane.

Regardless who is at fault, who will kena kemek when shit happens?

Too many only look at who is right or wrong in eyes of the law, ignoring whether you'll be alive after the fact.
Now the moto lady cannot go pangsai ever again, does it matter if she is right? BMW driver can still pangsai in jail.