Is "betrayal without any shame" a typical behaviour on borderline patients?

Possibly, not always: It can be, but it also can be typical of other diagnoses. Being without shame when deserved can also be linked to one with sociopathy. However, borderline is a very complex diagnosis and borderline behavior is often described by others as having to "walk on eggshells" and not knowing what to expect. Betrayal may be seen as justified by a borderline, as with a sociopath, hence, no shame.

Yes : Due to their stressful childhood and lack of coping skills- BPD pts attack others and have little regard for their feelings, moods, thoughts. Stay away or limit contact with such people. Set clear limits with them and stand behind your word. They will respect you for it. Dont be afraid to contact the police or fire dept if need be.