When Danielle Chang discovered she had superpowers it wasn't a huge leap for her to start considering superheroics. Although her powers were more defensive than offensive, she still thought she could make some sort of difference. She didn't really train though. She just went out there and did it. She never learned how to fight. That's something that could be seen as a huge mistake but it turned out to have less of an impact than it would be for most people. She could get up from just about any attack. Her ability to completely tank hits made her a more formidable opponent than she otherwise would be.
Danielle still mostly doesn't know how to fight. She improvises her way through situations. It pretty much always works for her because most of the threats she faces are manageable. But today is different. This villain battle has gotten more out of hand than she would like.