Is there any possibility you could ask her to wait 6 months? Is there any way you could beg and plead and tell her to please wait 6 months, that you both need to talk about this, that baptism is like buying a house, or getting a 30 year mortgage that you need to be OKAY with the decision together as a family.
Buy yourself some time, offer her a vacation to Mexico, a cruise, something where the two of you can talk without constant interruptions and bring some REAL literature with you. Make her read Crisis of Conscience, ask her to read the book and if she still feels like she wants to get baptised that at least you will feel like she's informed.
Please buy yourself time.