Is it correct to say “it’s the dress you tailored for me. These people swore not to send me my pictures” what does it mean and can it be rephrased?

Yes, the sentence is correct. It means that the speaker is referring to a specific dress that someone adjusted or fitted (tailored) for them, and that certain people promised not to send them the pictures of that dress or the event associated with it. Here’s a rephrased version: “It’s the dress you made alterations to for me. Those people promised not to send me my photos.”