Only typical Japanese I can think of, is that maybe you said something wrong and instead of telling you directly, she prefers to avoid confronting you by giving you the reasons and instead just stops talking to you.

But cutting off internet contact happens in other countries too. Without meeting someone for real, it's easy to put someone out of your head without considering the effect on the other.

Try to see internet as a good way to make contact, but don't take it as a substitute for real contact. Don't fall in love until you know someone for real!