And for your question. If it was me i would buy a 20in, but you should buy what you think you will be more comfortable on. Dont waste your money on the wrong bike, a 26 and a 20 are completely different bikes and riding styles, so i personally think you should make the choice.
She wants to sell the bike ASAP, but I've got to get new glass/contacts, apply at some schools, and my trail bike needs cranks and a headset, as well as a wheel laced up.
I was thinking I'd buy a 20" to have around for the days when the trails are muddy and I want to ride something other than my road bike. Since I've heard (and felt) how different 20" are as compared to 26", I thought I might give it a whirl. I really liked the ability to manual much easer on a BMX, and I need lots of work on manuals. Even just riding around the bike for an hour I could tell a BMX would be much more flingable than my current 26". I think most of that is due to the weight and geometry of my current ride.
I really should find out what I'm getting back in taxes, because if its what I think it will be, I'll have tons of money to build/buy what I want.