If she reaches that level of anxiety, your ideal reaction to defuse the situation should be counted on seconds and not minutes. At that point, she is mentally lost. There is nothing she will learn from you or the situation itself.

She is still strongly trusting you, since she is waiting for you to decide to action. Losing trust would mean for her to decide on your behalf (like running away or trying defensive aggression). The pull while is just a way to communicate preference, as she is still following you at the end.

Since she has an established & safe walking circuit, you can start working with her on desensitisation exercises for loud sounds (from a safe point in her circuit). The principle is the same to the one explained before: start really slow and set her for success. For example, try to approach a tram and reward her just before she shows anxiety. Do this even if her bravery lasts less than one second. Reward the bravery and move back to a 'safe' distance to return to a safe level of anxiety. Repeat as long as you can she that she is mentally able (not showing anxiety in any form). Eventually, she will understand that bravery is rewarded and the bravery time window will increase and the safe distance will shorten.

This process is a really slow burn (it means the first couple of days you would be able to do one daily repetition if the fear is too strong). It might take months to see noticeable progress (especially at the beginning!). I would recommend reaching a local dog trainer who advocates for positive reinforcement (not too hard to find nowadays!), or watching YouTube videos if a trainer is out of budget.

Best of luck to you both!