So my boyfriend has recently started contacting his half sister from his father whom he doesn't know. Thing is, they've been talking non stop for a month, and I'm just getting so jealous. She's texting him non stop and saying things like: "you're the best thing in my life right now" and "I don't know what I would do without you" and it's driving me mad. The thing is, I know this is a really bad thought pattern to have, but for some reason I can't get it out of my mind. I don't know what to do...