For that amount if work I think the expectation is or certainly should be that you would be paid. If you were to do it for free you would be going far above and beyond imho.

I think your plan to refer out for implementation makes sense. You help out your friend without getting yourself involved in something big you don't want to take on.

I would though also wonder how close this client is to your friend. It isn't her, it isn't her friend, it isn't even her father. To me this sounds like a strictly business transaction, she might even see herself as helping you out, not vice versa, thinking perhaps you might like free lance work.