Why are (some) people giving the OP a hard time? (And giving the posters who are on her side a hard time too?)
People are entitled to feel slighted and aggrieved at anything they choose, without being chastised or told to get a grip/get a life.
And as so many posters are saying they take 'you look well' as 'you have gained weight,' there must be something in it. I think this too. In some instances, It IS an underhand way of saying 'you are fatter than last time I saw you.'
Some people may not mean anything bad by saying 'you look well' but some people DO say it as a way to imply you put on weight. I have had people say it why I have gained weight, and I know that is what they are hinting at.
I once had a neighbour of my parents tell me 'hey golden, long time no see. You look well. You look better now you've gained some weight.'
I was so fucked off I could have knocked her out.
What's more, why does anyone have to comment on how you look anyway?! 
Another thing I hate is when people say 'you look different.' My friend's brother gets this. He left a workplace he had been at for 20 years back in 2009, (when he was 44,) and since then he has let his hair go white (he dyed it for years after starting to go grey at 33/34,) and grown a (white) beard, and gained 4 stone. Every time he sees an ex colleague, they say 'oh hi Steve. OMG you look different,' with a
look... or 'you got fat!' Or 'what the fuck has happened to your hair grandad?' 
I also have a friend who went out with her daughter last week to see an aunt they hadn't seen for a year. The aunt said to her daughter 'ooh hello Chloe... You're growing fast. I didn't recognise you. You look like my neighbour's grandaughter; you've got the same big round face.' 
So fucking rude. As I said, why comment on how someone looks anyway? It's rude, and rather obnoxious. And also utterly unnecessary! Whether it's a comment on their grey hair, their weight gain, or their weight loss, or whether it's that they look 'different...' 
People think they deserve some kind of medal for telling someone they lost weight. As I said, why do you need to comment on someone's appearance at ALL?
And as I said, cut people some slack who are offended .. they are entitled, especially if they have been slagged off, criticised, and scrutinised when they were growing up (often by their family/their parents.)