Dear AAC Team,
When arranging my mother's funeral in New Hampshire, I was told by her pastor that cremated remains may be buried, even buried at sea, but may not be scattered. They should be buried as a whole.
In some times and places, the Church has allowed some exceptions to the usual practice. There are some cases in which a person's body is buried in one place, but some part — perhaps the heart — is buried somewhere else. Famously, the composer Chopin was buried in France, but his heart is entombed in a church in Warsaw. In Montreal, St. Andre Bessette's heart and his body are entombed separately within the same basilica.
As Christians, we believe in the resurrection of the body. This is part of the "last things", which include the last judgment and the end of the world. When a person dies, the soul continues to exist apart from the body, and at the end of the world, God will raise us up again, restoring our souls to our glorified bodies. The world will be transfigured with us into a "new creation".
The Church has been cautious for a long time about accepting cremation and scattering of ashes. Both of these are funeral practices that can appear to diminish the identity of the body. There's a reason for this caution. Unbelievers have at times used cremation as a way of expressing their disbelief in the resurrection of the body.
Therefore the Catechism of the Catholic Church makes the point that cremation is acceptable as long as it does not represent a denial of faith in the resurrection of the body.
Here are the paragraphs of the Catechism about the disposition of the body:
2300 The bodies of the dead must be treated with respect and charity, in faith and hope of the Resurrection. The burial of the dead is a corporal work of mercy; it honors the children of God, who are temples of the Holy Spirit.
2301 Autopsies can be morally permitted for legal inquests or scientific research. The free gift of organs after death is legitimate and can be meritorious.
The Church permits cremation, provided that it does not demonstrate a denial of faith in the resurrection of the body.
So cremation has become permitted but I expect that there are probably not many dioceses where scattering of ashes is allowed.
The funeral service for the deceased is not complete until the burial of the remains, so whether the burial is in Illinois or in Colorado, your friend should contact the local pastor to find out whether she has an obligation to fulfill.
If she needs to arrange for a burial, she can make arrangements at a suitable time for her and her family, and the pastor can check with the diocese to clear up any uncertainty about what is permitted in that place.
I hope this helps.