From the 2nd pic, I could see the leather is very soft, as well as the texture appearance.
I had seen a fake one (for around HK$3300) and compared with my real one. I could see the leather felt like vinyl when touched, and its so hard that the bag looked like a box even it is empty inside. Also the hole and the hardware dont match. So whoever uses a fake one is unwilling to let others touch the bag.
But anyway the best way is to have it checked by reseller
If your sister feels uncomfortable buying from the seller then don't buy it. If she really wants a Lindy she has to visit the shop regularly. It's all about luck and patience, if she's desperate then buy it from brand off or Milan station.
From the first photo it looks pretty legit to me. Why do you guys think it's fake? If the photo was taken with the bag sitting on the orange box and dust bag would you think it's real then. As someone mentioned before you really have to see the bag in person before you can determine the bag's authentity. If unsure then take it to brand off.