fit a secret/keep secret warm

[frindle2]

Hello. Would you please tell me what "fit a secret" and "keep her secret warm" means in the context below?
Does it mean "You can't hide a secret in a backpack?"
And one more. Please tell me what "keep her secret warm" means.
Does it mean 'not to say her secret to her mother?'
Thank you.


--------from a children's novel, Honest Truth by Dan Gemeinhart
The counselor would probably try and talk to her. The counselor always tried to talk to her.
But there was only ever one person she really wanted to talk to.
She was afraid that somehow they would all know. She could hide it from just her mom’s eyes,
or just his parents’ eyes, or the police. But there would be so many eyes on her, all the time.
You can’t fit a secret in a backpack.

------------------------------------------
"Why do you think he ran away? Seems like a terrible thing to do to his parents, after everything they've been through."
Without thinking, Jessie blurted out her answer. Maybe it was because she was tired.
Maybe it was because she didn't want her mom saying bad things about her friend, not then.
Or maybe it was because her heart couldn't hold on to the weight of two terrible secrets.
"Because he's dying," she said, her voice flat.
"What do you mean?" her mom asked through a mouthful of food.
Jessie felt her eyes fill with tears but she blinked them back, pushed them back down inside her to keep her secret warm.
"I mean the cancer's back. They found out last week, after the tests."

 

[Skrej]

Hello. Would you please tell me what "fit a secret" and "keep her secret warm" means in the context below?
Does it mean "You can't hide a secret in a backpack?" Yes, that's an accurate explanation.
And one more. Please tell me what "keep her secret warm" means.
Does it mean 'not to say her secret to her mother?' Yes, but it also means keeping her secret in general, not just from her mom, but from everyone.
Thank you.


--------from a children's novel, Honest Truth by Dan Gemeinhart
The counselor would probably try and talk to her. The counselor always tried to talk to her.
But there was only ever one person she really wanted to talk to.
She was afraid that somehow they would all know. She could hide it from just her mom’s eyes,
or just his parents’ eyes, or the police. But there would be so many eyes on her, all the time.
You can’t fit a secret in a backpack.

------------------------------------------
"Why do you think he ran away? Seems like a terrible thing to do to his parents, after everything they've been through."
Without thinking, Jessie blurted out her answer. Maybe it was because she was tired.
Maybe it was because she didn't want her mom saying bad things about her friend, not then.
Or maybe it was because her heart couldn't hold on to the weight of two terrible secrets.
"Because he's dying," she said, her voice flat.
"What do you mean?" her mom asked through a mouthful of food.
Jessie felt her eyes fill with tears but she blinked them back, pushed them back down inside her to keep her secret warm.
"I mean the cancer's back. They found out last week, after the tests."

My comments in blue above, but you were pretty much correct with your guesses.