I think you're looking way too deep into this. I genuinely dont think that's his girlfriend. It could be a family member or close family friend. None of the other pics on that account indicate anything towards a relationship with Sid. Sid's not even in any of the pics so I'm not sure where you're getting this from lol
I do have a doubt that he has someone special in his life but if he wants to keep that under wraps then thats his personal choice and we should respect that as his fans.
Welcome to the forum btw, hope to see you around more 😊