Getting baptised is not a minor formality to progress your relationship. Once you are baptised your life is no longer your own.
My advice is - do not get baptised under any circumstances.
Good advice.
Obviously her family are giving her a hard time about you even though it's none of their business. Sounds to me like she is used to being controlled and told what to do. You both are old enough and mature enough to have your own kid each, so she should be old enough and mature enough to live her own life on her own terms.
If it were me i wouldn't be standing for this shit, make her an ultimatum. Either you're together or you're not. If she wants to let her family control her relationships then let her leave and you find yourself someone stronger.
If you got baptized you're handing your control and your balls over to her family AND the Watchtower Society. Baptism in this religion isnt like any other religion were you can walk away later without reprisals.
And think of your kid. Your kid will be expected to live in that mental prison too.