How to get over this?

Hi all,

This is my first time posting here, and I'm not entirely sure how to go about things, so I guess I'll just jump right in.
I'm an expatriate, (born in England, raised in Canada), who is now living in Italy. I love it here, but I have found it difficult to make friends, as there is a language and culture barrier that is difficult to overcome.
About 5 months into my time here, I met a woman who was simply supposed to be my new language tutor. We had/have a lot in common, from both living in foreign countries, (she was born here, but spent 7 years living in the United States), to our birthday, (yesterday was actually our birthday...she is 2 hours older than I am...small world, I know), to our values and opinions on things...basically, we just clicked, and our relationship went from an educational one, to a friendship to romance.
We spent almost all our free time together and I thought grew very close to each other. We would do everything together, from simple dinners and walks around, to going to Venice and everything in between. We spent a lot of time.
This past summer, I had to go back to Canada twice within a month of each other, (first time for a week, then I came back for a month, and then the second time was for the entire month of August). When I came back in September things had changed. I couldn't get a hold of her, and whenever I did, there was just short answers to things. I figured that she had "moved on" and whatever, and while that hurt, it's a normal part of life, and I did my best to move on from it.
Basically from September to January, I had seen this girl twice and heard from her, (emails or texts), maybe a half dozen times. Nothing to write home about.
Now during our time together, she had lost her job, so I, (looking back on it now, rather foolishly) had taken her CV, (or resume) into my school in the hopes that maybe she'd be able to do some private tutoring to those who needed it. I took it in one day, and she didn't hear anything back, so we both figured that nothing was to come from it.
Until early this month, when I walked into school, and literally turned a corner and bumped into her. She had been hired to replace another teacher who is on medical leave. She hadn't even bothered to let me know that she was working at the school and this could happen.
Now with Valentine's day just passed, and our shared birthday just yesterday, I had been dreading these past two weeks, but seeing her 3-4 times a week has really thrown me into a funk. I just can't shake this....feeling....just this dull ache in my stomach...whenever I think of her, I feel like garbage, and whenever I see her, it takes all I have not to turn the other way and leave, (which isn't a possibility, nor is it professional).
I've also recently found out that she is talking about me indirectly...she'll approach coworkers of ours and instead of calling me by name, she'll say "your friend" or "the Canadian guy".
The thing is, I truly believe I am no longer in love with her...I just feel abandoned by her, and extremely hurt by her behavior. Not letting me know why we stopped seeing each other is one thing, but to get hired at the school, when I set that up for her, is another thing completely.
So basically I am turning here to see if anyone has any advice on how to handle this? Getting back with her is out of the question, and I just need to know how to...deal...with this without feeling like a complete wreck whenever I have to have any contact with her.
Sorry for the rambling nature of this, and thanks for any help anyone can give.