Nagging bitch
A nagging bitch is someone who texts you like it's a sport and she's trying to win the gold medal in the most annoying messages.
'You didn't even say you'd come, so I'm sending you 100 messages about it.'
'You're not even here, but I'm still texting you about everything.'
'I know you're busy, but I'm still going to send you 50 messages about it.'