ToME: the Tales of Maj'Eyal

How do you get Melinda in the fortress? I only saved her once (the other times I reached her I was too slow or felt more like loot than heroism), but after that I just never saw her again.

In addition, is there any mechanical benefit, or is it just to have her around?

Talk to her father / herself - the bottom shop in Last Hope.

Being a saving grace for a poor victim intentionally provides no mechanical benefit (and, arguably, big detriment; and, not arguably, great hassle), so that it is a moral choice and not a choice between two benefits. Likewise, telling escorts to go away.
Yep, go to her house, and you can talk to her, as said above.

Great sales pitch, 0player, but I kill off the lumberjacks after getting rid of Ben Cruthdar. ToME isn't a game where I let silly things like morals get in the way of all my murder.

Thanks for the info, though.

You need to talk to her AND get her to go on a date with you.