Thank you both.
There are a couple wrinkles I guess.
One being, the ashes have already been split and her ex-MIL has already paid for an urn for me. She asked me when she started making arrangements about a month ago and I said Yes. I don't feel comfortable refusing them now that she has come out of pocket for me.
Secondly her kids live in another state now. Their father did not live in the same state we did and I have not seen them since she passed. We've talked about them coming for a visit but it hasn't progressed past that.
I have some internal guilt that if I don't accept the ashes or have a ceremony for her then I didn't "truly" love her. I know this is my own mind but I feel as though I may be judged.