women are more...

[Joe]

We often say that once a woman is in love with a man, she wouldn't change her mind easily and divert her love to another man. It is relative, men more heart-changing than women. My question is, is there a word or phrase for that? For example,

Women are more _____ than men.

If you wouldn't say "Women are more _____ than men", what would you say? Thanks. :)

[Tdol]

We have 'fickle-hearted', but I'd be careful about saying it.