It could be she wants to leave it up to you. Or she wants to avoid it so badly she’ll wind up leaving it up to you.
When I asked my dying spouse about what he wanted done with his body after he was gone he first quoted me some stuff about Klingon culture (which was very much Mr. Broomstick, he’d been a Trek fan since the original series), then stated he did NOT want to donate either his body to science or organs to anyone else (though with cancer there wasn’t a lot that would be suitable for that anyway). Everything else was up to me. So, in fact, I started shopping for cremation services before he died. That way, I had a plan in place for when he was gone.
Which is how I handle these things.
If she’s not going to open up about what she wants done afterward then it WILL be up to you (presumably - I’m assuming you’re the decision maker). In which case one option is to plan “Unless mom says otherwise I’ll do X, then Y, then Z”. You can then continue to gently ask mom her preferences and change accordingly, but if she still refuses to state a preference you have something mapped out.
That’s the option that works for me. It’s not an option that works for everyone.
I also spent a half an hour with a lawyer going over state laws regarding deceased spouses, what I was and wasn’t legally responsible for, options, and items to consider. It turned out I had already covered most points, but I found it reassuring because I was not functioning terribly well the first couple weeks afterward.
What I’m really saying here is that if your mom refuses to discuss this with you, you are still allowed to discuss how you will cope with/deal with things on your own with a social worker or lawyer. If, for example, she won’t give you her banking information and she passes away what are your rights/responsibilities and how would you go about informing a bank that you are the person responsible for dealing with her estate, if you are that person (I’m assuming again). Mom still has the option to take control, but that way, if she doesn’t, you’re not struggling to deal with these issues while in the midst of your grief.
Again, that’s what I have found works for me. If something else works better for you, by all means go for it.