She knew that it would fuck with him, but she didnโt care obviously or else she would have kept it private. She tried to cover up the fact that she did an awful thing by blaming the break up on Macโs sobriety issues.
After two years, Ariana grande broke up with Mac. A few days later she was already dating someone else. A few weeks later she announced publicly that she was engaged. She didnt give a fuck about him or his well being. Nobody moves on that quick from the person they โlovedโ