Hard lesson learned, but make sure you reflect on this experience and what you can learn from it.
Why did you apply for this new job? For friendship? Socialization? Because you were bored? I'm guessing the answer is no to each of those. Most likely, you accepted this job because it provides income that you need.
I don't mean to minimize the importance of having good support at work, or to suggest that you can't be friendly with co-workers, but you made a critical mistake of assuming too much familiarity with someone at work. Someone you were just getting to know.
I know it can be lonely starting a new job, but when you are on the job, you have to put on your work face, your professional face and remember why you are there.
In the workplace, it's best to keep your opinions to yourself, and if you have questions, direct them to your mentor or supervisor. Doesn't matter that she's not warm and fuzzy. She's not there to be your friend. She's your mentor.
Some people in the workplace, supervisors and mentors included, are difficult people to deal with. It's just a fact. You have to learn to deal with all kinds of personalities, the nice ones, the backstabbing ones, the flaky ones, the fake ones, the domineering ones, and the crazy ones. Every workplace has them.
I'm not trying to be mean or dismissive of your feelings. Most people would feel hurt or betrayed by what happened to you. What I'm trying to stress to you, however, is that you must go to work and realize you're there to perform a function.
That said, I realize how valuable and necessary good friends are. Do you have good friends? It's so important to have people we CAN confide in, share experiences with, etc. Work hard to reconnect with friends you may have lost touch with. Try to cultivate new friendships by joining groups outside of work with others who share your interests (book clubs, gardening clubs, sports groups, arts/crafts groups, etc.). Good friends and people who support us are crucial to our well-being. Life CAN feel overwhelming, and even more so when you feel all alone. Please do whatever you need to do to strengthen existing friendships and develop new ones.