The reasons behind your friend's behavior may not necessarily have anything with you. During the holidays your friend may have been busy with family and other activities. If the two of you had not had any disagreements, it may be better to just wait a few more days. Your friend may have also not brought their phone where they had gone or are preoccupied with things and waiting to be free to reply to you accordingly.
For the time being, try not to personalize the lack of replies from your friend and wait few more days to see how things progress. You can still let your friend know that you're thinking about catching up with one another when the two of you have the time, and that since you did not hear back, you were concerned about their well being.
It won't help to personalize it. You do not have to let her behavior slide; just find out more before concluding about what is going on. If you've already expressed concern to her, she is ultimately the one to shed some light onto why she's behaved this way. You may also inquire about if anything is going on in her life that would have gotten in the way, ask her if she feels the communication was taking a lot from her time or things she had to do, etc. Then, you can still point out to her that if she is not going to be available for chat sessions to please let you know so you can make other plans accordingly.