Kinda late but... Haibara/Shiho is still a teenager as well... AND she and Shinichi conflict against each other... Shiho would rather run away and be safe without caring about strangers getting hurt. She always advises Shinichi to not get involved and just let the BO kill other random people. I understand that she cares for him, but like... she's not giving any thought to the victims. Shinichi just jumps into things to save other people, not caring about his own life, as long as the people he loves are safe. Those two actions fight against each other xP Shinichi and Ran's different traits/actions can fit together, but Shinichi and Shiho's traits/actions are KINDA the same but they act against each others'.
And Shinichi's only lying to Ran to keep her safe. He can't tell her EVERYTHING. People need their own secrets. Anyway, he also TRIES to lie to Haibara but she eavesdrops on him talking to Agasa about stuff related to the BO every time... So he can't lie to her