If she's going away on vacation, she might be have been more busy recently preparing for the vacation - taking care of things at home and/or her job. I wouldn't worry too much about it.
I think you should just send a short text before she leaves wishing her well on the trip. Then, when she gets back pick up the phone and call her to see if she wants to continue seeing her. Don't worry about seeming too clingy. You're over-analyzing her reaction to things that really aren't that big of a deal.
“This planet has - or rather had - a problem, which was this: most of the people living on it were unhappy for pretty much of the time. Many solutions were suggested for this problem, but most of these were largely concerned with the movement of small green pieces of paper, which was odd because on the whole it wasn't the small green pieces of paper that were unhappy.” ― Douglas Adams, The Hitchhiker's Guide to the Galaxy