We've seen Sara's reaction to being brought back, but we don't know how everyone is going to react to her presence. Thea and Laurel are obviously shaken by how she acted when she returned, but the latter is also going to be happy to have her sister back. As for the others, well it probably won't be so straightforward. Felicity will no doubt be welcoming, Diggle will be wary, and you imagine Oliver is going to be rather pi**ed off when he realises exactly what Thea and Laurel have done. In fact, I can quite clearly hear him angrily asking Laurel: "What have you done?" or "Do you have any idea..." Then there's the matter of Quentin Lance. He hasn't had an easy time of things as far as his daughters are concerned, and he's got a lot on his plate right now with Damien Darhk. If/when they break the news to him, just how is he going to respond? It probably won't be a happy reunion.