Okay people are being way too melodramatic now. Amber is not manipulating Sophie, even if she gets her drunk one night that is not manipulation it's just stupidity. That happens in october, SOPHIE then spends two months deciding she wants Amber and not Sian. It will be all Sophie's choice completely. The spoilers haven't even indicated manipulation on Ambers part. I think some people just don't want to accept Sophie will be moving on and so are trying to make Amber the sole bad guy here.
That isn't what the Sun spoilers said or what the shows insider said. They said
Sophie's feeling for Amber win out. Now we haven't seen the storyline so we can't for sure say what part Amber will play but there is nothing to suggest she's forcing Sophie into anything. It even says Sophie freely kisses Amber during their second kiss and that is why she is so guilt ridden. You aren't guilt ridden unless you know YOU did something you shouldn't have. Yes, she can blame Amber for the first kiss, but not what comes after. It's apparently Sophie's letter to Amber that gets her caught by Sian, not Ambers letter

(if that spoiler is true as it came from here). But it is Sophie who stops the wedding, it's not like it's Amber running into the ceremony ala The Graduate and screaming at Sophie not to get married - though that would be hilarious.
Of course Amber is automatically partly to blame because her kiss set things in motion, but Sophie isn't two, she can make her own decisions. She is the one who will decide to break Sian's heart, no one else. She is the cheater here. So she should be the one getting most of the blame for Sian's pain. It's like suggesting Molly was completely to blame for the break down of Kevin and Sally's marriage, poor little Kevin was manipulated into getting her pregnant