Who's next?

So, today I was in line at one of my favorite stops for lunch and I happened into a situation in which I'm not sure if there is an etiquette rule, but there should be. There I was, so hungry I had already begun counting down how many seconds I had left until my stomach literally ate the rest of me. Then, out from the restrooms, a woman started to head my way. She was unremarkable - the standard skirt suit, work badge,and high heels that grow on trees around where I work. She continued to walk closer when I realized she was taking an incorrect path to get BEHIND me. Surely, she was not going to get in line in front of me?!? At that point, my stomach would likely be forced to eat her. So, I made direct eye contact and edged slightly forward. Her response to this? "I'm sorry, I have to be rude and cut in line to join my friend." You what?!? First of all, I hate it when people say "I'm sorry..." and then continue on with doing the exact voluntary action they were reportedly sorry for. Secondly, announcing that you are about to be rude does not indeed make the act any less rude. It is sort of like when someone says "don't take this the wrong way, but..." "Don't take this the wrong way, but have you thought about using Rogaine?" I'm not even sure I could take that the wrong way. Unless you are an actual door to door Rogaine salesman, there is only one way to take that. Sorry, back to my point. The way I see it, this woman had 3 options - to cut me in line, to be temporarily separated from her lunch buddy, or for her lunch buddy to get out of line and join her behind me. It seems like there should be some sort of rule about this. Today, it was just me getting cut. But, what if there were 5 people behind me? Is it cool to cut all of them? I guess what confuses me is why going to the bathroom is not grounds for losing your spot in line? It's not like I can walk halfway to the front of the line and say "Hey, I stopped by the bathroom before I left my office, had I not lost that precious time, I'd be right about here in line. So, I'm going to go ahead and jump in." Although, if I see this lady in line again, I'm definitely going to try it.