Did she leave a will? Sounds like her death was sudden and she might not have made formal arrangements.
I understand your pain, OP.
It is so important to make plans and talk to your family members. I have already made a list of heirlooms that go to each child. Even now I occasionally mention that the china goes to X, my wedding ring to X.
I do not want my kids to have to make these decisions. It often leads to hard feelings that sometimes can't be mended. We had many heated agruments with my dh's siblings after his mother died. His sisters wanted me to sign a paper saying I would not take any heirlooms if I divorced my husband. I gladly did because I didn't want the old junk anyway. Of course, 10 years later, we are the only ones who are still married. Very ironic, lol.
Have you talked to your mom's spouse. She might not offer money, but she might be more than willing to give you some keepsakes.