so I assume we're back on track for our original plan

Why would you assume that?

I told her this isn't normal

Nothing I've read here screams "abnormal" or "codependent". Saying so feels like a reach

she chose to appease her mother over the commitment she made to me

She changed her mind to do something with her mom instead of you. It wasn't a commitment, it was a suggestion and then she changed her mind. I don't see what you're seeing.

From what I'm reading, soft YTA. It seems like you're letting your resentment cloud your judgement. Nothing I've read seems particularly unhealthy or abnormal. Nothing I've read seems like it's sacrificing the happiness or health of either your girlfriend or her mother. It sounds like you feel trapped and uncomfortable no longer living alone, and are unhappy it isn't just the two of you and your girlfriend is doing a lot for her mother.

Suggesting couples counseling is fine, but it's not your place to tell her that her relationship with her mother is unhealthy or "codependent" unless something seriously toxic or damaging is going on, which it doesn't sound like.