would have been happy vs could have been happy?

[keannu]

Can you tell the difference among the 3 sentences?

If I had given her a Christmas present,

1. she would have been happy.
2. she could have been happy.
3. she might have been happy.

My previous similar question is related to would's willingness, but in this case it's more related to presumption. So does 1 have more chance than 2 and is 3 the least chance?
I'm curious which of the three native speakers choose when they say depending on situations.

 

[5jj]

If I had given her a Christmas present,

1. she would have been happy.
2. she could have been happy.
3. she might have been happy.

My previous similar question is related to would's willingness, but in this case it's more related to presumption. So does 1 have more chance than 2 and is 3 the least chance?
I'm curious which of the three native speakers choose when they say depending on situations.

As I have suggested in the other two threads, you are trying to get too much at once. It is difficult, without more context to know how you arrive at 'presumption', and whether you mean to apply this to #2 and #3. It's probable that the chance of her hypothetical happiness is greater in #1 than in #2 and #3, but we really need more context.