It sounds like you two need to have some very serious conversations. You can start by emphasizing that you want to build a stable permanent
future together. Have you considered pre-marriage counseling, or going through FPU together, or something? You’ve got a temporary arrangement right now and to combine for life you need to be on the same page about money.
DR was talking about Christmas spending on recent podcast. The desire o be a giver comes from a generosity of spirit, but you don’t want to have your holidays lead to a “financial hangover”. You want everyone to be able to wake up the next day and feel that it was a great holiday with no regrets.
About the email – I would write it all down, but think about how your partner best communicates. Some people like getting the distance and space you get with email – I am one – but other people find it cold and can feel blindsided. You know your partner the best, what’s the best way to have a serious discussion with her ? And also be open, because after 15 years she probably has her own set of concerns. You want to have space to let her bring up issues too, but be able to take one thing at a time without it turning into a fight.
I really liked John Gottman’s book “the seven principles for making marriage work”. It’s also good to have a counselor or pastor lined up to help, because once you start churning up emotionally laden issues it can get heavy fast.