Sadly, there won't be any events until Yasa becomes an adult. They only happen when there's at least one adult on the island.
Was Yasa already the chief when she was left alone, or was she made chief afterwards? It's too late now, but she might possibly be better off as an ordinary tribesperson. Although she would lose the daily benefit of the magic food she would at least be able to farm when she grows up.
If you haven't already I'd suggest you put the game on slow speed. That cuts down on the amount of food consumed per hour. I don't know the actual figures, but, if we say that she eats 24 units on fast speed, she would only eat 6 on slow. Since mushrooms are worth 6 units no matter what the speed (35 for red ones) she should be able to find enough mushrooms to start building up a stock of food. The daily allowance of magic food comes every 24 hours, no matter what the speed. I'd also suggest you pause the game before closing, when you can't look out for mushrooms.
On slow speed she should stay alive at least until she grows up. Then she'll only have any stored food plus the magic food to live on. You'll just have to start hoping for an event to bring one or more companions (at least one male). There are several tales of tribes surviving against the odds, so DON'T GIVE UP!
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To err is human; to arr is pirate.