It's basically a projected assessment and representation of your business. There is this link http://www.ehow.com/how_5081725_writ...ness-plan.html but it doesn't fit the bp breeder mold very well.
You can easily leave out and adjust things to make them fit though. It's just a nice backbone to base a discussion on. Give her solid information, over-estimate costs, and be honest. Show her where you have come since you started,
and where you could be with the right investments. You might be surprised when answering some of the questions, and seeing your financials on paper (or excel )
Treat this subject as an investment / business opportunity..not as an "But it's so purty I WANT!" (even though it is...soooo purrrrtyyy) Being adult about the situation will go a long way me thinks.

Also, perhaps ask her how much she feels comfortable with you investing into a new project. Try to take her suggestion into serious consideration etc. Make sure it's a 2 sided discussion so you know she's not just shutting you down in her mind / not really listening to what you are putting on the table.