This question already has an answer here:
My wife and I are applying for UK visas. How should I answer the questions about money?
Must all the questions about my money that are required to be in GBP be answered in GBP?
I have stated in my application that we are traveling together. How do I answer about her expenses in the UK (how much the trip will cost her)? Should I reduce my own expenses by half and show just her costs?