A boundary is "I can't do this" An ultimatum is "you stop or *threat*"
Best advice I can say is let her do her thing and it works for her or it doesn't. She needs to choose to come back so give her the opportunity to miss what you both had.
In the mean time go hit the gym, go for a run, get a tan, get new hobbies. This is also your time for growth. I would recommend to carefully choose your texts, voice mails, emails, etc.. save all records for court. Avoid excessive alcohol use as well, it is a depressant anyway
"Don't chase people. Be yourself, do your own thing, and work hard. The right people - the ones who really belong in your life - will come to you. And stay." ~ Will Smith
