I couldn't get into the Rachel Morgan series by Kim Harrison for ages due to not being able to identify with any of the characters, especially Rachel herself. A lightbulb moment occurred when I realized that witches in that universe have a maximum natural lifespan of 150 years or so, compared to 100 years for humans. So even though Rachel is 24 years old at the start of the first book and is physically matured to that age, she is emotionally 2/3 that age, or about 16. All of her choices in the first five books in the series are made by an impetuous teenager and it isn't until the sixth book or so (two years later in the timeline, when she's almost 26 physically and therefore almost 18 emotionally/mentally) that she starts fighting her immature impulses and acting like an adult. Because she's only just now becoming an adult in her mental development! - Abstruse
When Rachel is on the boat that blows up she complains that the protection charm on the necklace didn't work, or that it only protected itself... but she survived a boat being blown up! She was saved from drowning! Considering that it was Jonathan that pulled her from the water, I can't think of anything short of magic that would enable that to happen. (Yes I know that Trent told him to, but the whole set up is so bizarre and unlikely that it actually makes more sense to say that it was subtle magic that the necklace was manifesting than that it all just happened to happen the way it happened.)
It's a surprise to Rachel when her mother approves of her relationship with Nick despite him being a human, because her mom wants grandchildren. Later it turns out that Rachel's father was in fact human and adopted her. Her mom understands because she made that choice herself.
Early in the series it is shown that Ivy uses a sword in her enforcing duties. Later in Ley Line Drifter knowing that she will be facing an psychotic sword wielding semi-immortal she faces her barehanded. Did she just forget to bring it or did she want more of a challenge?
Algaliarept makes an agreement to not harm Rachel or her family. It is said that the penalty for breaking the agreement is being put in a bottle to serve Rachel. Later in The Outlaw Demon Wails he attacks Rachel why doesn't she demand he be put in a bottle?
It was a few years down the line. Even if Rachel remembered it, by the time she did an arrangement was already set up with Algaliarept. Why risk alienating your new demon bestie?