I was just about to mention that---the reason he's choosing to make use of his right to remain silent, whereas NK chose not to, might just come down to their individual will-power. LE probably didn't have enough info at the time to convince DE he should talk, but by the time they talked to NK, they probably knew the two were together on the day NL went missing or knew she had some knowledge about her whereabouts based on the 'POLICE' text she sent him. They probably didn't have that kind of knowledge to use as leverage when they arrested DE. LE can, and will, lie to suspects to get them to talk. They might have said something like... "look, we've already spoken with DE and we know you two were together that night. If you scratch our backs, we'll scratch yours." Then, she probably said the bit about not wanting to go to jail and they probably told her if she helped them find NL, she might not go to jail but definitely would if she didn't. So, she started talking.
ETA: Although... I am surprised that she told them as much as she did and admitted her level of involvement... even if she's still not being completely truthful.
ETAA: Maybe that's why she looked so pissed in her mugshot photo? Because she thought LE would let her go if she gave them information but then got arrested anyway. She has little to no deductive reasoning skills if she actually believed she wouldn't go to jail but it's possible, I suppose.