Absolutely not. Your sister is overstepping boundaries and if she's going against them and disrespecting you like that then she needs to be cut out of your life. I'd be absolutely fuming over this 😒
Your not unreasonable at all. I wouldn't allow haribo either, requires a lot of chewing skills and your sister was out of line. My sister did similar Christmas day. I was feeding my son his lunch and she handed him a creme egg hero after I said no twice. I quickly took it off him. Which made me the party pooper. I set the boundary firmly after that. My husband was raging at her and was glad I reacted as he was going to say something a lot worse than I did.
I wouldn't be happy either - aside from the choking risk, there's no need for a one year-old to be eating sweets as they're so unhealthy. Ultimately it's your child so you get to decide what they eat and it's not up to your sister to decide whether you're being reasonable or not.