I would not offer a refund but perhaps offer to send a couple of extra samples to make up for her disappointment.

I know this might be a pain but what I would do in future ads is wait till I had remnants ready, then put them together in lots, photograph them and sell them that way.

What is in the photo should be what they get.

I personally realise 100g isn't much, as a buyer I wouldn't have been expecting a lot, but some buyers honestly have no idea. Your ads need to be more explicit-show the actual samples and approx sizes of each sample.

I know some sellers favour this 'random bundle' method of selling but it often ends badly. As a buyer, I still recall many years ago I bought some doileys like this. The seller showed a table covered with about 20 of them, most embroidered and a lot quite good sizes. The ad said buyers would get 5 random doileys.

I bought a bundle and got one small embroidered one in my sample, all the rest were plain and fairly small. I was disappointed. i gave good feedback, but i was disappointed and felt a bit cheated. I guess you can tell by the fact that all these years (about 14) after the event, I still feel annoyed.

I can't think of anything more likely to annoy a buyer than to leave them with the impression that what you advertised was better than what you doled out to them.

Don't do it to yourself would be my suggestion. Not unless you are prepared to go the other way and send MORE & better than a person would logically expect.