Who ever knows history, can't trust Bulgarians. That is if u are a Serb, don't know about others. I'm sorry this girl of yours has to read this stuff cause there must be a lot of people in your country that are decent and honorable. Anyway, here are some facts ... which are coming from my poor knowledge in history but those are all facts and truth...
1. 1913 Second Balkan war - Bulgarians against Serbs, Greeks and Monenegrians. Becuase of that orthodox people lost the only chanse to take one half of Constatinopol.
2. 1914 First World war - Under the influence of Austrougarska monarchy, Bulgarian invaded south Serbia and Macedonia. Because of that Serbian army and a part of the alliance went through Albania with a lot of loss in men. This is the worst thing they've done to Serbia!
3. 1941 Second World war - Bulgarians are joining the pact with Musolini and Hitler in order to attack Serbia and after German ocupation, they go in to Serbia and kill a huge amount of civilians. However, after war is finished, Bulgarians seek for new patron and they soon find one in comunist block.
4. 1948 Bulgarians make diversions on Serbian borders from 1948 untill early 60's under dictation from Moscow.
Newer history is well known... they have recognized Slovenia, Croatia, BiH, Macedonia and Kosovo among first.
In many cases it can easily be recognized that Bulgarian political elite is making political acts on the contrary of Bulgarian regular people, which includes your girlfriend
)