why don't you ask her? ultimately she's the one who put on weight and she's the only one who can figure out the real reasons she's gained weight. if you can have a conversation with her about while being tactful and noncritical, you may actually help her address the issue. with that said, weight is a very touchy subject with women so tread lightly. also be aware that most women have periods where their weight fluctuates for many reasons. again, she'd know better than anyone else.