There is a woman in my community that attends some zoom shuirim classes that I attend. Her mother sometimes attended one of the classes. She doesn’t know me. Her mother passed away. Is it weird to pay a shiva call to this woman?
Not weird at all. very thoughtful. just don't stay overlong (whether you know her or not) and obey all other etiquette rules of shiva like not showing up at 8:55 pm if shiva hours are from 9 am to 9pm.
What I remember most clearly from my shivas --aside from folks who told me amazing stories I never knew about my dear departed--were people who hung around all day (trust me, NOBODY appreciated that)or showed up at 9 pm and stuck around till 11. When it says shiva hours are X am to Y pm, it means that before Y pm you skedaddle, not "last customer will be seated at Y pm."