My Female Friend started to ghost Me suddenly - after I called her "Sister" !!!

This is in no way a Karma Farming Post, as I am quite Confused !!! Currently, as a 26M, I've been friends with this girl (25F) since 2017, back in my college days. I was the typical introverted **“glasses guy”** with a reserved personality, while she had a tough, dominant attitude but a kind heart—basically a real-life **Tsundere**. Despite being polar opposites, we bonded over video games, horror, and comics. We often hung out together, leading some people to suspect there was something more between us. But as someone who never saw love or romance as his thing, our friendship always remained ***strictly platonic***. Over the past six months, she’s been calling me more frequently, mainly to seek advice about her career, life struggles, and moods—something I’m generally good at handling. Meanwhile, as I worked on becoming more social and confident, she noticed the change and started making playful comments about my looks. Since I am described as a **"Fair Skinned Dude with Glasses, a Tall n Lean Body Structure** (used to be Underweight in the Past) **with a Light Beard"** She’d tease me, saying things like, ***"You’d look so hot and handsome if you hit the gym, gain some muscle, and upgrade your wardrobe."*** Since she often called me "Bro" or "Bhai", I never took it seriously and just saw it as friendly banter. However, three days ago, we were texting on WhatsApp about career-related stuff when I casually started my message with "Sunn Behen (Listen, sister)". After reading my texts, she suddenly stopped replying. Today, I double-texted, but she still left me on read—something she has never done since 2017. I’m completely lost here. Why is she suddenly ignoring me? **What just went wrong?!**