How to make a Knitter's day

A couple of weeks ago a new coworker found out that I knit. She and I talked about it and she expressed interest in learning sometime. She told me that a friend of hers had sent her some yarn a while ago to try to encourage her to learn. She wanted to give the yarn to me because it had been in her house for a long time and she knew she wouldn't ever use it. I said sure (who wouldn't??) and didn't really think about it further. Today she told me she was going to bring me the yarn and I didn't know what to expect. I thought maybe it would be a skein or two, enough for a scarf or toque & mittens. I didn't know what kind of fiber to expect, but I can tell you what I didn't expect:



10 skeins of Green Mountain Spinnery Mountain Mohair in Blue Gentian. Enough for a sweater.

(I'll wait a moment while you either seethe with jealousy or gasp in delight)

I was so excited and told her I would make her a sweater with it. She insisted that I wasn't supposed to make something for her with it, it was for me. So I told her if she wouldn't accept a sweater for herself made with this yarn, I would make her something with some other yarn instead (we argue back and forth "No, you're working too hard, let me help you" all day long. It's refreshing really).

So, I'm looking for suggestions for my windfall and also ideas for something I can make to return the favor. Any thoughts?