I am impressed by your dedication to save this one girl that is hard to like.
However contracting is not the only danger in the world. She can be assaulted and killed or put in a coma. She could fall into a witch's barrier and get kissed or eaten. Or she could be bullied into committing suicide.
The world is a dangerous place, and you cannot remove all the risk to all people, but you can lower the risks.
In this particular case, she should contract, just with a different wish than canon! She may not want to turn into a monster, but she'll never be happy as a charity case for a magical girl.
Also I would like if you would realize that most of the posters do indeed wish to help her, they just don't see her in any unreasonable danger, while others may be.