I would say clearly slim. No more than a size 12 at least.
I don't buy clothes as a present anyway but my Son's Grandmother (Dad's side) is very thoughtful and has brought me some items of clothing as presents for years.
Before I had DS I was a size 10. Got clothes in a size 10 and never thought anything of it.
Then I put on a lot of weight and after labour while in hospital she bought me a nightdress in a size 18! I still feel hirt just thinking about it.
She bought me a dressing gown and pjs in a size 16 the following year.
Now I've lost most the the weight I am being given size 14 clothes. She absolutely didn't mean anything malicious. She's lovely!
Generally though, AIBU to think you shouldn't buy clothes for someone who is overweight? I found it hurtful personally.