Matt
We had someone nearly take us out on my son’s first trip. My wife had a few choice words with the driver who was genuinely mortified when he realised what he’d nearly done. He was a bit younger and it didn’t really phase him for long.
All our early rides were almost completely road free (cycle tracks near but not on main roads) so he got used to vehicles being near but not too near. Now when he’s on the back he’s happy on the road even with quite large vehicles.
As for getting her back on, it might be an idea to leave it a week or so then get the bikes in the car (if necessary) and head for somewhere traffic free for a few confidence inspiring rides.
Also does your partner / wife ride? Even if she can manage a couple of miles and ride next to you entertaining little one that might help.
Our son likes to sit on the cross bar and be wheeled round the garden holding the handlebars or sitting on the ‘big boy’ seat and being held in one arm while the other’s used to push the bike. With lots of positive reinforcement and encouragement he’s developed a real liking for two wheels and I think it’s the big boy thing + child seat.
He’s just under 2 by the way and been coming out on the bike for about a year but not always without tears (helmet not producing smiles!).
Do you know anyone else with a kiddy similar age and a child seat who you could meet up with who would be a good influence?
Not sure if that’s any help at all, just our experiences.