OK, so here is my take. Tesla the feelings of jealously are yours to own , and realistically yours to deal with, Nothing has really happened yet, yet here you are ready to tear a head off and in tears. You can say things like i was brought up this way and so on, however every one of those things are just excuses.
You need to get down to the base emotions you are NOT dealing with and deal with them, at the current rate your jealous behaviours are destructive and will ultimately break down your relationship, based on what you said its starting already.
Go talk to this guy,(her bf) just bring up what your feeling, invite him out or over for a coffee and just talk, you will probably find it easier to do once you start.
BTW once you do get past these jealous feelings and you can love many it really is a wonderful place to be. Also if you really want to talk I dont mind talking on the phone.