Sewer Line Replacement Urgently Needed

My friend in Morningside is selling her house and was required to fix her sewer trap in her basement for inspection. It turned out that her sewer line needs to be replaced under the sidewalk as well! She already paid a big chunk for sewer trap and now she is being asked to pay 10k for sewer line repair on the top of it! She is desperate for any advice how to lower the cost of something she was not even aware of when putting her house on market. Any advice would be greatly appreciated.