I can't speak for anyone but myself, but I never liked Riley before there ever was a hint of Spuffy.Poor old Riley , his character was the first to suffer so we could have Spuffy
Riley was the only person who Buffy knew who might have any way of helping Spike. It was the Initiative who put the chip in his head in the first place, so her logic there is understandable.Why did Buffy get in touch with Riley to get out Spikes chip but not tell him about the thousands of Turkey hams and her great plan of taking a bunch of girls to kill them?
As to why Buffy kept the general goings on in Sunnydale at that moment secret, why she didn't try and recruit help from Riley or his teammates, or, for that matter, anyone who she thought might be willing to come, including Angel and his crew and every benevolent demon in the area, I have no clue, unless she feared that bringing in outsiders might in some way undermine her authority. Not the best of decisions on her part, if you ask me.