my mom is against the CIO method

My parents are visiting from out of town & God knows I love them... but
They don't agree with my CIO method for my daughter. My mom freaks & cries when I do it. She calls it abuse & gets mad at me. 
My LO has been co-sleeping with us because it has just been the easiest thing for all of us. We've been on/off co-sleepin since birth & she is now 8 months. Sometimes I'll have her sleep in her pack n play (which is right beside me on my side of the bed) & I'll have her in there all night after her last feeding. My hubby & I would really love to transition her into her crib & we're starting out slow. We want her to be able to fall asleep on her own without the help of mommy's boob. But honestly I'm so thrown off by my mom's voice that I don't know where to start. 
Please help... Thanks in advance!