First- if I were your neighbor I'd be think I'd be offended about the notes something about it rubs me the wrong way.

None the less, the same thing happened to us (pooling fecal-smelling water by the garage door). Sounds like she needs her line drained, thats what we needed. And the line that the plumber accesed for us was at the front of the house. (Who would have thought??) First we called Best choice..they fixed it once and it happened again. We called them again (since they fixed it before) and they claimed we needed the whole line leading out to the street replaced (~$4000 job). Untrusting we called Roto Rooter who fixed it and we have not have a problem since.

Since she seems to be ignoring the problem I'd follow the advice of other to contact L&I.