As long as she seems happy to hear from you when you call, I don't see an issue with it. Its hard to read a person though when they are in another country so I could try to be aware of hints, if she says she has a lot going on in a week with homework be aware of that and probably not call her as much. Maybe shoot her an email before bedtime saying you are thinking of her and hope she's doing ok. I don't think you are being too clingy. Like I said, when she comes back you'll want to spent time with her but keep in mind that relationships need for both parties to have their own lives.
So, so you think you can tell Heaven from Hell,
blue skies from pain.
Can you tell a green field from a cold steel rail?
A smile from a veil?
Do you think you can tell?
And did they get you to trade your heroes for ghosts?
Hot ashes for trees?
Hot air for a cool breeze?
Cold comfort for change?
And did you exchange a walk on part in the war for a lead role in a cage?