Tan, I think you have done very well with Izzy! Wish Laila would go to sleep that easy too! But I can imagine that it's frustrating you in the afternoons. Our bub has that too but it's usually between 6 and 7.30 pm, or onwards! (My ratbag is 7 weeks today).
Maybe you could be onto something in regards to her shortish sleeps during the day?? Maybe they are just a bit too short and it builds up until she is overtired during that grumpy time??? (I have no idea really- sorry!) So maybe try and get her to go and have a bit more sleep at her nap times??? That doesn't help much does it! I think what I would do is similar to what you do, I would stick her in her pram, and go for a walk down the park or somewhere nice. Use that time for a bit of exercise! Then, wait till she grows out of it!!

Sorry not much help really!

Whats your secret to getting Izzy settled so quick anyway!??!!!

All the best