Ember Store Push to Model within Model

I have a relationship setup between my models like so...

A {
 a1: undefined,
 a2: undefined,
 B: {
    Cs: [{}],
    Ds: []
 }

A contains basic attributes, and has a model B that belongsTo it. Model B hasMany Cs and hasMany Ds.

Typically you push to the store doing something like this, and it would update the model A in store to have a1 = 'blue'.

store.push({
  id: 0,
  type: 'A',
  a1: 'blue'
}

How can I push to the store to update a specific item in Cs, or Ds?