When I check my game I only have 1 villagers and she only 4 year old she is weaken because I have no food

If the child is the only one left alive, your options are very limited.
1) You can get her to find/pick mushrooms whenever they pop up. Brown mushrooms are worth about 8 food points and red mushrooms are worth about 45.
2) There's a very small chance that an island event might result in an increase in food supply.

Well I read that adult can cause island event but not thr children

I found 1 brown mushroom.8 food altogther

I found another brown mushroom.16 foods altogther

Good, keep it up. I hope you can keep her alive until she reaches 14.

Island events can happen to children.
Good Luck!

I just had a similar thing happen to me in a game I recently started. Though Cheop was 12 when I found him.

I found mushrooms for him to pick to build up the food supply. At first I had it on 1/2 speed to try to spread out how often he needed to eat in comparison to how often he found mushrooms.

When it was really low, I would put the game on PAUSE and then just wait for a mushroom to popup. (He didn't age during that time, but he also didn't weaken any more...)

When he turned 13, I figured I had enough food for him in order to put the game on 2x speed in get him to 14 more quickly and let the game run for an hour.

I came back to an Island event (500 food in a crate!) and Cheop was ready to work!

He farmed "over night" and has plently of food (the adults managed to get the farming level 2 before they died), so he is researching today while I'm at work. I'll be going for level increases in science (to earn more points per research) and medicine (to help him live longer) before any other the others (even to bury the adults) in hopes that an even with infants comes along soon.

P.S. my event occured after Cheop "came of age." I read on this forum that events won't show up with only kids in the village.

Kiki my villager is weakened so what can I do.She is 4 year old

Kiki ate 2 food.14 foods left.