my friend asked me if her boyfriend is planning on proposing to her

About a month ago my friend who I babysit for boyfriend told me he's planning on proposing to her and told me how he's planning on doing it! Today she asked me via text if he told my husband and I his plans to propose but told me I didn't have to answer her question. I don't know how to go about this... I want to answer her question but not exactly tell her the truth so she can be surprised when the time comes... help? Lol