Girlfriend sounds bored on the phone lately, is she losing interest?

So I have been seeing my girlfriend of 9 months now and whilst we live in different cities we get to see one another a few times a week. When we are together everything is great and we say how much we are compatible with one another and often talk about a future together. What's bothering me lately is that when we are not together she has become a little quiet. In the beginning she would be blowing up my phone but the last couple of weeks I hear from her maybe once or twice during the day. We talk every night on the phone but the last few nights I have noticed that she sounds bored/uninterested in our conversations and she is quite busy at work these days and it's late when we talk but still, I have bad anxiety and I'm just wondering is this normal in a relationship?

Also last night when she said she was tired and going to sleep I saw she was online an hour later, this made me question things even more?
Girlfriend sounds bored on the phone lately, is she losing interest?
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