Clearly, she is not the right one for you. Maybe good for a
short fling but long term? nah. She is just playing with you only.
It's the female ego at work here.
She wants to feel that having a boyfriend in her life makes her
feel satisfied in life. In other words, she is an attention-seeking
person. For all you know, this new boyfriend might just be a
stop-gap solution for the time being. Or it could be she wanted to
get rid of you so she could be with the new boyfriend. In any case,
you don't want to be with such girls who play such mind
tricks.
I can understand how incensed you can get to be out with an
ex-lover who is accompanied by her boyfriend. Now it becomes you
are the lightbulb. How sensitive she is!
doko