Girl is online on Facebook chat, but hasn't "seen" message. Is she ignoring me?

Both girl and I are college students. We started dating right before the end of summer. She is back home overseas for the summer so we are essentially in a long-distance for the past 3 months. We've been talking everyday, catching up on each other, sometimes flirting, but the past few days has been weird. She'd reply in short responses, take hours to respond.

I've sent her a FB message saying hi. She's clearly been online, but hasn't "seen" my message. Does this mean she's ignoring me/losing interest?
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+1 y
we haven't been talking for 2 days now...
Girl is online on Facebook chat, but hasn't "seen" message. Is she ignoring me?
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