mom not into her own kid ???

So I know someone in my family who recently had a child through a serget. The baby is adorable! However, the mom is never really involved...she's always calling baby sitters to come watch her kid while she goes to parties in LA and out with friends and to work out. I know she didn't give birth to the child so maybe she didn't get those hormones to be connected but I just don't understand why they would spend all this $ on getting a child when the mom would rather just hang out with her friends and go to LA and have her mom watch her child. I just don't understand this because I'm 19 would be way more into the baby then the mom is and she's 35! I just don't understand this as a women, what are your thoughts ??