She sounds like a real biatch Cuppy, so here's what to do. Find a product called "Ant Rid", it's a sweet dark colored liquid that dissolves in cola, coffee, tea etc, and doesn't have any unusual taste or smell.
Over a few weeks, with a couple of drops in her drinks each day, she'll get weaker and weaker, and if she doesn't give in to your constant cajoling to "gift" you the 550, keep feeding it to her, and she'll reward your efforts (something new in your relationship, apparently) by eventually expiring. This stuff is really hard to pick up in toxicology tests, so it probably won't be noticed during the autopsy. Just to be safe though, make sure you get her cremated...........
I imagine that her life insurance will cover the mortgage and any other outstanding credit you have, you give her kid back to it's father, and you keep the house, the Ducati, and those other bikes. If you can't find Ant Rid in the US, PM me and I'll send you a couple of bottles.