Dating someone my brother and sister don't like

I (28M) started dating with someone (26F) my brother and sister know from their time sportsclub a few years ago. For a few years I've thought she was beautiful but never really talked to her. Since a few months we've been sending a few messages back and forth about a mutual interest. A few weeks ago we started flirting and dating and it's been super nice until this point. I really like her and believe there might be a future in this.

But... I casually dropped her name a while back to my brother and sister at a moment when there wasn't anything romantic happing between me and her. Their reactions were strong to say the least. My sister who shares a few friends with her said "She acts nice and playfull to everyone's face then turns around and becomes shit"

So... Ofc my brother and sister have no say in who I date. But at a certain point I will have to tell them and best before they hear it from someone else. Any advice for that?