Advice - 13 year old DD - would you call this bullying WWYD?

DD and her BFF have been inseparable since they were 4 years old. BF has form for being possessive - she hated DD talking to or having other friends. DD worked out how to handle it and they bumbled along well.

When they started high school, the wheels fell off. It was expected as they were put in different houses. At first it seemed ok, the girls seemed happy enough. Then one day BFF blanked DD. No reason given, she just point blank refused to speak to her. This went on for 4 months. Eventually she decided she would speak to DD again.

Roll on another year. In January BF decides yet again to blank for an unknown reason. She upped the ante by being really mean - things like walking up to DD in a group, pointedly greeting everybody and just giving DD a filthy look.

Things got worse when BF started telling people that DD had been saying she has terrible parents. My DD loves her BFs parents as her own and was extremely upset about this. I spoke to her mum - a dear friend, who said she would talk to her.

DD came home so upset yesterday. BF is telling all their mutual friends that they aren't friends because DD is possessive and that she hates her. She is making her life miserable.

Would you classify this as bullying - given it's been going on for 18 months?

Looking for advice on how best to handle this? WWYD?