Does she have them on both arms, or just the one? If both, that's exactly what a skin removal scar looks like. I've only seen her show the right arm. There's no reason I can possibly think of why a gastric band would nearly cause loss of limb OR result in scarring like that. I really think she just had the tiniest bit of loose skin, and privately paid to have it removed rather than jumping through the hoops that the NHS would have made her go through (I'm assuming similar to US insurance, they'd want to see sustained maintenance of weight loss, but ALSO evidence of participation at a gym to build muscle tone under the skin as that can disguise it, although skin laxity can't really be fixed). I don't know what NHS regulations are, but she would've had a very, very, very hard time getting approved for skin removal in the US and would've needed to self finance. Skin removal is really only seen with people who have lost hundreds of pounds and who it's affecting mobility and physical health. I'd think the "poor me" attitude might be because maybe she didn't expect them to be so obvious.
Note: speculation, NOT body shaming, personal knowledge only, open to correction, and I wouldn't fault Sophie for any of this if she weren't fibbing about it