This book will focus on the rights each spouse has under certain laws, situations, and circumstances, and how the division of the property will be decided by the court or through negotiation.
Seems like it would be up to the lender. I would think since your spouse is part owner, the bank cannot get a lien against your house to secure the loan without her agreement. But if the lender is willing to lend you money without a proper lien, then that's their choice.
My guess is that they my file a lien, but your spouse would easily be able to invalidate it by showing that they did not agree to it as a joint owner. Then you would personally be liable for the balance of the 2nd mortgage, but the lender could not seize the house if you defaulted.