Question

diane, who has little patience, started aggressively swinging her shopping bag at the woman, who was walking too slowly in front of us.

remove the comma between diane and who.
remove the comma between patience and started.
remove the comma between woman and who.
no change is necessary.

Explanation:

The clause "who has little patience" is non-restrictive (adds extra info about Diane, not essential to identify her), so it needs commas around it. The clause "who was walking too slowly in front of us" is restrictive—without it, we don't know which woman is being referred to, so it should NOT have a comma before "who". Removing the comma between "woman" and "who" fixes the punctuation error.

Answer:

Remove the comma between woman and who.