Why do people just ghost someone for no reason?

A friend of mine from high school (let’s call her Janelle) just suddenly stopped talking to me. She stopped talking to me on November of last year. Last time we talked was I November and we had a great chat but she answered with short answers. So November I texted her to see how she’s doing, BUT she hasn’t texted. I thought she was busy so I left her alone. Then two weeks later I texted Janelle again, STILL no response. I kept texting her every week but NOTHING. Then I stopped for a couple month. She wouldn’t answer. I don’t know if it was something I said. Then I decided to try again in March. I was like, “Hello. Why haven’t you been answering my texts? If it was something I did or what I said, I’m sorry.” But NOTHING. Then today I decided to try one more time. I was like, “Hey Janelle girl, how you doing?”
Then 15 minutes later, she texted, “Hey there! 🙂 Who is this please?”
When I told her it was me, she didn’t answer back. It’s been five hours!
I’m about to give up! WHY WON’T JANELLE ANSWER ME BACK?????!!!!! 😡😤🤬😖👿😡😡😡😡🤬🤬🤬🤬