how to respectfully approach a coworker about their bad smell?

well, it is the manager's job. he should call her into the office, and use the "sandwich effect". like so, "donna, you're a valued employee, you bla bla bla very well, and your bla bla is superior. i do need to address something with you, though. some people have complained about a particularly strong odor that seems to eminate from your cubicle or person. what can we do to alleviate this problem? we really appreciate your hard work and positive attitude..."

something like that might work.

I agree - the group meeting is a terrible, terrible, awful idea. I think you need to employ a stranger, or maybe a consultant - someone who comes in for one day and mentions something. You don't want her to think that everyone in the office has been talking about this for a long time. She'll die of embarrassment. Bring in an acting rude tech support person and have him say right to her something direct. That should be enough. If you think that's too immature, then the manager should say something quietly and only to her when no one else is around.

The best way to address this issue is to have the human resources office and or her manager ONLY, privately meet with her, probably near the end of the day when most of her co-workers are gone. If you don't have an HR office, her manager needs to address the odder issue as if he/or she noticed it and not mention that her co-workers have been talking and complaining about her oder.

The group meeting is a horrible idea, although your intentions were good.

This is one of the downsides of being a manager. Managers have to tackle tough situations like this one.

The trouble is, body odor problems can have complex origins. Daily bathing or showering, plus freshly laundered clothes from the skin out, is basic. But sometimes odors arise from sweaty shoes, coats that haven't been to the cleaners in months, or household smells the person has no control over. Even tobacco, alcohol, medications, and certain foods can cause body odor.

My suggestion: Help your manager research causes and remedies before she speaks to that worker. So-called "deodorant" soaps are not usually the answer. They may suppress one type of bacteria that cause odor, but that just allows other types to proliferate. It's like using weed killer to get rid of dandelions, only to see crab grass take over.

It's nice of you ladies to try to address the problem without making your co-worker feel bad. But people get de-sensitized to their own smells, and she may not even realize she – well, reeks.

Don't have a meeting about her

I think direct approach in a friendly discreet manner would be best. Maybe one person should do it because if confronted by a group she might get embarrassed.