NTA. It's not cheating to sleep around while you're single and haven't promised any exclusivity. If she had a problem with it back then, she should have backed out of the relationship, not marry and have kids with you.

It's not uncommon for addicts to blame other people for their problems. She's bringing up your past actions to deflect from her current ones.

Don't let her shift blame and redirect the conversation. Her drinking (and in this case, child negligence) is the issue at hand, everything else is irrelevant.

Getting drunk whilst watching your small child is not okay. Until she's willing to get help, you need to be in the mindframe that you're a single father and do what needs to be done to protect your child's welfare. You wouldn't trust your child with an alcholoic babysitter. This is no different.