If their first time is True Love, then the Hunger dies. It doesn't matter if the first feeding is fatal. Irwin and Connie didn't have true love, but the feeding didn't kill Irwin because he has so much life force.
I just reread the parts of Blood Rites where Thomas talks about the first feeding, he says that the first feeding is always fatal.
That White Court kids are like any other kids until their Hunger wakes up, then the danger comes to them, but apparently there is a choice. However that's a bit vague, Thomas says they are forbidden under Lord Raith's orders to explain that to the kids, so they have that first feeding, killing the victim and are hooked. So apparently Jim altered that explanation. I could include quotes but don't have time this morning but I will if you want. Harry did burn Inari when she tried to feed on him and Thomas explained that one as well. He said that if true love passed between him and in this case Susan during sex though it was over a year in the past at the time Blood Rites came out and he was with no other women, he was protected by that love. So you'd think because Harry and Murphy had sex in Peace Talks that Harry should still be protected, but he isn't.

Connie didn't kill Irwin because he had too much life force? Really? You'd think it would be a banquet for Connie's Hunger Demon and it would want even more. I thought that was the point when Harry fed Lara's Hunger demon, so is Connie now slave to Irwin? We know from Summer Knight that Harry was severely depressed after Susan left him and felt guilt and self loathing because he couldn't find a cure for her, this went on for months, yet the true love that passed between them the last time they had sex was enough not only to burn Inari, but to burn Lara five years later.. So Lara's claim that she had just fed and canceled out the protection doesn't compute, neither does Mab's explanation that Harry's current state of grief, self loathing, and guilt hold up. Only other explanation is that true love hadn't passed between Harry and Murphy that last time. Something had changed, no final reading on the soul gaze because she died before Harry could get a reading on how she really felt. Yeah, that one left vague on purpose, you'd think the first thing Harry saw as brief as it was would be her final thoughts of love for him. One thought is maybe getting a Holy Sword broken in her own arrogance and being so badly injured had altered Murphy's feelings somewhat, maybe enough to affect the true love she supposedly felt for Harry. Makes sense if you go with Mab's explanation, maybe Murphy was going through some guilt and self loathing of her own in those last days. Wouldn't be the first time, she took to the bottle for a while after Nightmare got finished with her.
Also in the final pages of Blood Rites, it is explained to Harry that if Inari and her boyfriend truly love each other during that first sex act, it will block her Hunger demon, and apparently just burn it out, freeing her forever from it. Which if what Lara says in 12 Months is true, it has, Inari is happily married with three normal vanilla kids.