disabled senior threatened with utility lien

My disabled, senior citizen mother recently had her income cut in half. We've struggled to keep up with her bills, and are current on all but her sewer bill, which went up to $2,000 because of a catastrophic emergency water leak, which is now fixed.

We've spoken with the sewer authority several times, explaining the situation and trying to set up a payment plan, but the only agreements they will accept are still far beyond her ability to pay right now. Now, they're threatening her with a lien on her property.

Is there anything we can do about this situation, to get them to accept payments she can actually afford? We're scared to death she'll end up homeless because of this.

Thank you in advance so very, very much to anyone who can give us some advice.