Zoom echo of own voice during screen share

[SL5]

During a one-on-one foreign language lesson on a zoom meeting, when the teacher shares her screen, when I speak my voice comes back to me on a slight delay (one second or so). A word spoken alone usually doesn't come back. But anything more than 2 words does. This does not happen when screen share is stopped. Nor does this happen on other zooms I do where the other participant shares her screen share. The teacher does not hear any echo or otherwise know this is happening, except after I told her. The teacher says no one else has complained of this issue -- she does private lessons with four other students on zoom as well. I am on a laptop, using system speaker and microphone. I have tried using an external mic, turning off original sound, and asking the teacher to mute while I speak (I thought this may have worked once, but it did not the last time she muted her zoom -- I saw the red mute symbol go on). None have worked.

I gather that this is likely because my voice coming through her speaker is then picked up by her microphone, and then sent back to me on delay. The recommendation I have received is to get the teacher to wear a headset, but that is not happening. I have tried a suggestion on reddit, which was to go into Zoom Audio - Advanced and set Signal processing by Windows audio device drivers to "Off (Windows - raw)" but that also has not helped. I welcome suggestions. If there's anything I can do on my side, that would be ideal. I could probably make a few requests of tweaks on her sound, but my ability to do so is somewhat limited. I don't know if there are echo cancellation settings, or anything else I can request of her (ideally, simple and easy for follow).