Girl I like hasn't responded to my Christmas message?

I like a girl who works within the same shopping mall as me, our stores are almost next to eachother, just 1 shop between us. We interact multiple times a week and have done consistently since about March this year, i really like her and she seems to like me.

Anyway, on Christmas day i sent her a nice Christmas message on facebook messenger, its now been about 36 hours and she hasn't even opened the message. This is also the very first message I've sent her.

In person, she seems very bubbly and open and happy to interact with me, and all is very positive. I also never really see her scrolling through social media/on her phone, but occasionally she'll be talking to someone on the phone, but even thats not that common. I think she is just a bad texter possibly?

Should i be worried about this?

Updates
6 mo
Forgot to add. She recently took 2 weeks to respond to her birthday messages on facebook, and almost a month to accept my friend request. Im guessing she doesn't spend much time on social media.
Girl I like hasn't responded to my Christmas message?
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