If support was always beneficial and there were no problems linked to it, topics like 'helper syndrom' or 'codependency' or even worser forms like 'Munchausen syndrome by proxy' would not be a problem. Those are only 3 negative effects of 'support' either affecting the person who supports or the person that receives support. I do not think there is a clear line that can be drawn between support and abuse or exploitation. There is also no clear line that can be drawn when it comes to perception. Even medical, psychological or social staff who observe such scenes might have problems to draw clear lines here. Somebody who supports might for example feel burned out, but they are still doing whatever they do, because they gain appreciation. So when all the sudden symptoms appear, they might misattribute the cause of those symptoms. Because there is no easy answer to your question this was in the first place split into several clinical phenomenons. Beside that there are surely hundred of different cases that have been legaly discussed. And even this I would say this is only the tip of the iceberg. One never knows what else is happening behind closed doors.