ALittleMop, why? I only meant that I couldn't be bothered starting a row over a tenner, not that I couldn't be bothered with my friend...
Stunned by all your stories on here. Guess there are "givers" and "takers"...
Bit of an anticlimax here, I'm afraid. She popped round in her lunch hour and we chatted about the kids and stuff and, when there was a lull in the conversation, I said, "So, what's happening with your phone then?". She shrugged and said she didn't know as she had three people interested. I took a deep breath, harnessed the power of Mumsnet, and said, with a smile, "But you're not going to sell it to some stranger on Facebook, are you? You're going to sell it to your lovely, kind, generous, babysitting-at-the-drop-of-a-hat friend because you love her more than you do an extra tenner, right?". She said, yeah, she supposed so. I'd made my point and left it at that. She is due to get her new phone on Monday so it'll be interesting to see what happens.
Thank you, lovely Mumsnetters, for helping me think through this and come at it (hopefully) from the right angle.