Is it selfish to leave a partner who has depression?

Today Niall spoke about an email we recieved from a woman who is married for 25 years. In the last 5 years her husband has been suffering from depression and she says it has got so bad she feels like leaving. She said at the start she was very supportive ad helped him as much as she could but now feels like the man she married is gone for good.

Would she be selfish to leave him? Is it supposed to be in sickness and in health? Or should her happiness also come into play?

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