Welcome to Yorkietalk. Questions are always welcome.
Put Lily in a car seat that has a hook for her harness. That will solve your car problem and keep her safer.
My boys bark at bicycles, but we are working on it. Desensitization is the best method to alter behavior. Don't pick her up when you encounter the triggers. Maintain a calm, confident demeanor. You can't fake it. Keep in mind that a dog has keen senses and picks up signals from you that you don't even realize you are transmitting. If you tense even slightly or breathe differently when you approach a barking trigger, you will inadvertently encourage Lily to engage in the undesirable behavior.
I have found that scolding does absolutely no good and only makes the dog more excitable, more likely to bark. Enlist friends or neighbors to do training exercises with treats. Work on passing people on the street. Start out with the person passing at a distance and gradually move closer if Lily is comfortable. Give praise and treats for good behavior. For undesirable behavior, turn around and make her walk in the opposite direction.
Training takes lots of repetition and time. YouTube has loads of great positive reinforcement training videos.
Another great way to desensitize is to take the dog to crowded places or different places. My boys get territorial when we walk only in our neighborhood and don't go on any special outings to other places. That is when they start barking at all of the interruptions on our walks.
Hope this helps. Good luck and congratulations on the new addition to your family.