Love / Don't want others to join us at a table - is it normal for Polish girls to get angry? [161]

I am in the early stages of getting to know a Polish girl (I am an English guy). Yesterday we have our second date, after spending some time together elsewhere we arrive at a bar. She sees one of her work colleagues who then joins us at our table and dominates conversation. When she leaves for the bathroom I try to explain to him that she is out with me and that I don't appreciate him taking all her attention. When she arrives back at the table, she is then very angry with me for doing this and tells me I can't tell her who she can and can't talk to. I am not trying to control her, but in England it is not polite to join a couple on a date. I'm very confused by this and had difficulty explaining to her as I was a little drunk and had become quite annoyed as I was very patient with this guy. Is this normal?