Is it wrong for me as a co-guardian to get in touch with a funeral director and set up payments for a loved one's funeral?

I don't see this as being inappropriate at all--in fact, it's very thoughtful of you to do. Some people do plan for everything, including their burial plots, caskets, flowers-basically the whole thing. My mother and dad did this, and when daddy died, it was so easy and stress free to simply go to the funeral home, make the very few last minute decisions, and walk away.

When my FIL died, it was like watching my hubby and his 2 siblings running on a hamster wheel. Absolutely nothing had been done to prepare. So. although it worked out in the end, wow, the stress was incredible, and the kids were completely overwhelmed by EVERY decision.

Make sure nobody else has already done this for her--and then go ahead. It is thoughtful and sweet of you to do this.

It is appropriate for you to contact the funeral director and discuss

Mom never set anything up? If something happens to you there should be a successor set up.