Aside from porting your number over to google voice and enabling call screening the only option is to work with the telephone provider. Sometimes telephone companies can trace spoof calls back to their origin. This can be a timely process and does not always provide results. Your best bet would be to have her block that number all together as it seems she is being targeted.
Information on Caller ID spoofing – https://www.fcc.gov/consumers/guides/spoofing-and-caller-id
Google voice call screening – https://support.google.com/voice/answer/9262934?co=GENIE.Platform%3DDesktop&hl=en