I was meditating on the word "Ishtar" for a few seconds this afternoon when it hit me: the reason why Amunet wanted to hide the Harsisis.

Now, in case you don't know, Goa'ulds have genetic memory. They have all the memories of all their ancestors. When two Goa'ulded hosts have a child, that child, a Harsisis, has all the memories of both parent Goa'ulds' ancestors.

So what?

Apophis wanted the Harsisis for his new host, presumably for the genetic memories, but he already had all his ancestors' memories. He must have wanted Amunet's memories. Now that's great and all for both of them, but Amunet must have realized at some point that if Apophis's new host had all her memories, she would be useless to him. And he could dispose of her. Because of that, she hid the Harsisis on Keb to ensure that she wouldn't be discarded like some minor shol'vah.