Some people love a good BB victim campaign don't they

it makes some feel like they're better people by fervently supporting them

Or they simply like to support a genuine underdog for obvious reasons (justice may be). Often the hm is the perceived 'bullied' hm (the target of the pack) but I feel it's increasingly looked for each series. At times they genuinely can be, but sometimes the hm can bring it on themselves imo as in jades case. Both jade and the twins are showing their true nature's right now and neither is pleasant.
For me I think some girls that feel they've been in jades place will sympathise with her too......ie she can't possibly be disliked for her personality....oh no..... so it must be jealousy regarding her looks of course.

All us female fms that dislike her are usually accused of being predictably ugly, reclusive and jealous, if we don't see her superior beauty.

Their can't possibly be any other negative things that we're all seeing coming from her.
And then of course people just like her, find her misjudged/misunderstood, see a different character deeper down, or think she's an integral/entertaining hm this series. There are many reasons really, even if some are personal or even hard to grasp at times. But we all have the right to our own opinions/fav hm. For me personally I think she's manipulative and vain, but at the same time she shakes the house up so right now I'm undecided whether she should go.
Then as others have said... some fans like a 'entertaining' hm that creates all the drama, likable or not. If Helen has support, anyone can.