People have been sued for injuries caused while performing CPR, so I could certainly imagine someone being sued for undressing a person (without their consent, obviously) to perform CPR.

You can sue anyone for just about anything. But it doesn't seem like a very winnable case to me. Maybe in some crazy jurisdictions. Many places have 'good Samaritan' laws that protect people who are not medical professionals when they cause injuries during a good faith attempt to safe someone's life. I would assume injuries to someone's modesty are included...

At the end of the day, would you rather let a woman in need of CPR die because you are afraid of maybe getting sued, with an even smaller chance of a conviction?

There's also the court of public opinion to consider, in which actual legal standing is irrelevant. Small comfort if you successfully rebuff a suit but lose your reputation in the process.

Not to mention the hassle and expense of defending yourself.

Of course, I agree. My point was just that it's not like my grandparent's suggestion that there could be consequences for the rescuer is unheard of.

In Germany not performing what we call "lebensrettende Sofortmaßnahmen" (stable side position, clearing airways, CPR) is (at least technically) criminally liable to § 323c StGB. I shall also point out that first responders have some legal protections and insurance.

Do you have a link for that? Every time I look into one of these/similar stories it is a shitty insurance company either heavily encouraging or basically forcing the suit if the person wants to be covered for their injuries at all.