How do I deal with my sneaky, two-faced, competitive mother?

My entire life, my mother has been competing with me. If I buy an outfit, she buys 2 of them. If I'm wearing anything cute, she goes "oh great, I have to change now - u can't look cuter than me." If I end a relationship with a friend, she becomes their best friend. She talks about everyone behind their backs & then is nice to their faces. Most recently, she has been texting & non-stop calling me about the fact that she can't stand my son's girlfriend & 1 of his friends, but then she invites them to the beach & is now friends with them on Facebook. She speaks horribly about my ex-husband's new wife & then invites her to do things together. She tells me we have to break my son away from his girlfriend but then tells my son that "your mother &father have NO SAY WHATSOEVER in who u spend your time with - it is none of their business. u should just move in with me & papa." Then when I decide I am done with the drama and cancel plans with her, she calls my husband to complain about me. Keep in mind, she won't EVER say anything directly to me. She calls me all the time complaining about how depressed she is & how she needs money & of course, I come running to her rescue, but then she has enough money to go to amusement parks & host beach parties for teenagers. I'm getting reports from my employees of the way she tries to talk my son into moving away from his parents, but she's always my best friend to my face. I can't take it anymore. I've had it! Is it totally crazy for me to cut my own mother out of my life?