HELP: This WhatsApp DP is about to end my sister's marriage

Please I need sincere advice on this urgent situation. I travelled to my sister's place to spend the sallah break with her family, from the very first day of my visit I sensed that things were not normal in their home; they were virtually faking every smile and obviously waiting for me to go back.

I pretended not to care...after all no be my family issue.

Unfortunately, just this morning at exactly 5:50am, hell let loose...
She and her husband were raining insults at each other. The major problem? Her husband posted a DP on his WhatsApp that got her angry and she refused to cook for 3 days insisting that he must apologise.

Please don't mind the typo errors, I typed it in a rush and with a sleepy eye. I was dreaming of my dream man when they woke me up with their husband and wife wahala.

Please what's the best way to handle this issue?

See the DP her husband use on his WhatsApp that she's crazy about:

Is this enough for my sister not to cook for her husband? How can today's couples live in peace?