My cat doesn't eat food muchmuch food.

Or "My cat doesn't eat very much".

She eats food, but always goesalways wanders off somewhere after having a bite or two bites.

However, she usually comes back to the bowl after about 15 minutes, and starts to eat again.

I wonder if she suddenly remembers she havesn't finished her food.

Can I also say "She goes somewhere, when she is halfway through eating her food"?

Yes! Maybe "After she's halfway done with her food she goes somewhere else for a bit."

My cat doesn't eat food muchmuch food.

She eats some food, but always goes somewhthen wanders would were after having a bite or two bites.

However, she comes back15 minutes later, she returns to ther bowl after about 15 minutes, and starts to then nibbles on her meatl again.

I wonder she suddenly remembers whether she haven't finished her food.

Can I also say, "She goes somewhere, when she is halfway through eating her foodoften wanders off somewhere, despite her found remains half-eaten"?

My cat doesn't eat food much(that) much food.

She eats foodwill start to eat, but always goes away somewhere after only having a bite or two bites.

You can also say:
"after only having a couple of bites"

I wonder if she suddenly remembers that she havesn't finished her food yet.

Can I also say "She goes somewhere, when she is halfway through eating her food"?

"halfway through eating her food" is very natural English -- great job.

You can use it like this:

→ She almost always wanders off somewhere halfway through eating her food

→ Halfway through eating her food, she often wanders off somewhere

My cat doesn't eat foodvery much food.

She eats food, but she always goes somewhere else after having a bite or two bites.

I wonder if she suddenly remembers she havesn't finished her food.

Can I also say "She goes somewhere, when she is halfway through eating her food"?

You can say "She goes somewhere else when she is halfway through eating her food" or "She goes away when she is halfway through eating her food"

In your sentence, I think a slightly more natural sounding translation of 途中で is "in the middle of." For example, "She goes somewhere else when she's in the middle of eating her food."

My cat doesn't eat food muchmuch food.

My cat doesn't eat much food.

She eats food, but always goes somewhere after having a bite or two bites.

She eats food, but always goes somewhere after having a bite or two.

I wonder if she suddenly remembers she havesn't finished her food.

I wonder if she suddenly remembers she hasn't finished her food.

Can I also say, "SWhy would she goes somewhere, when she is halfway through eating her food"?

My cat doesn't eat food much.

This is unclear as we don't know if your cat doesn't eat food very often, or if, when she does eat, she eats little food. I would recommend either:
"My cat doesn't eat very often" or
"My cat doesn't eat very much food" (Based on the rest of your text, this option seems best adapted)

She does eats food, but always goes somewhereaway after having a bite or two bites.

This is not incorrect grammatically, but I've just adapted to sound more natural.

However, she comes back to the bowl after about 15 minutes, and starts to eating again.

I wonder if she suddenly remembers she havesn't finished her food.

Can I also say "She goes somewhere, when she is halfway through eating her food"?

Yes, but you should change or qualify the word "somewhere". For example ""She goes away when she is halfway through eating her food"? or ""She goes somewhere else when she is halfway through eating her food"?

She eats food, but always goes somewhere else after having a bite or two bites.

I wonder she suddenly remembers she havesn't finished her food yet.

Can I also say "She goes somewhere, when she is halfway through eating her food"?

"somewhere else"