I don't think it's really that odd - she wants to help the poor people drowning. Some people have empathy for pixels that resemble humans/humanoids

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I've sort of done stuff like that before in WoW, but it's rare I bother. I know they're pixels, saving extras doesn't achieve anything, and they're just going to respawn.
She'll most likely fall into the same patterns as the other gamers as time progresses, but if she wants to do it, I'd give her some patience and leave her to it - I doubt she spent all that long doing it - even if it does seem awhile.
A good chunk of my time I spent time doing stuff that didn't achieve anything, but was fun to me. Some of the now-achievement-earning things I did before there were achievements (collecting pets, armour sets, mounts and questing in every zone - zone achievement didn't take long for me to complete when the achievements came out lol).
One thing about MMOs I like is they tend to be much more open-ended in terms of objectives than other games. Devs often put in extra things to do, which aren't necessarily going to "further" you in the game, but can give you a change of pace should you choose to do them.
When my hubby was levelling in WoW, at some points I grouped, at others I left him to do his own thing. Once she starts to find her feet and can operate on her own, I think it's important to see if she wants to quest together still or if she wants to explore a little on her own.