I think it's worth asking why the hobby is so male dominated though. Women, generally/demographically speaking, are just as interested in games as men are. In listening to a fair number of women talk about their experiences, many feel pushed away from games because the space is so male...
I think you've actually put yourself in a situation that not many people find themselves in. That is, you have players that are extremely emotionally invested in an NPC.
Life and death can be fairly transient in D&D. You could probably make them go on a quest to recover the soul of Snik or...
I think they can be a bit clumsy because of the tracking you need to do vs. single use expenditure in 4e. The trade-off for that is more flexibility and distinction between different classes though, which 4e felt a little lacking in. So I think from the player perspective it's comes out ahead...
This sounds like exactly the sort of thing that was written into the rules to encourage some story.
If I were you, in the future I would think about the personality of the villain. Then come up with what would be something traumatic enough to warrant the banish spell, and work the acquisition...