15 years old is not a toddler, she's a teenager. That's the point where they start looking to IM with friends and such. Even if she's not going to play games, running any decent version of office is going to be next to impossible on a P166 powered system.
As for learning about computers with windows 95, are you serious?? That's so far out of date it's not even funny. I gave one of my aunt's a computer that at least a P3 with a decent amount of memory, windows xp pro and office xp on it. She wanted to learn about computers (for potential new jobs), so it was better that she learn on what would be most common in the real world. Enough things are similar between xp and win2k that it would be a minor adjustment (some places are still on win2k for their business systems). The versions of office haven't changed too much in the way they work/function between xp and 2003, and the previous version. IF I had given her older items, it would have done more harm than good, since she'd have to learn more just to start a new job.
If a system doesn't at least meet the requirements for xp, don't bother with it... Otherwise, you're wasting everyone's time by even giving it to the person. Better off making some art with it (melting items and such) or seeing how far you can toss it to get it to break into small pieces.
As for being 'harsh', so is the world...