Why does this girl spy on me?

Ok so , there’s this girl. We’ve known each other for a few years now. We talk a lot every day. She’s seeing a guy at the moment but it’s early stages. She’ll keep spamming my phone even when I’m with a friend there’ll be a 3 different WhatsApp messages a Facebook post that sort of thing. She’ll spy on my WhatsApp stories. She’ll seem to get jealous if I’m having a coffee date with another girl , but she says she’s not in to me. She’s even spammed me a few times when she’s been with this guy.
Why does this girl spy on me?
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