Spoof Text of the Dead?

Story goes like this:

My aunt had just landed at the airport and was texting my mother about the state of traffic and how long she thought that it would take her to get to Grandma's house. Then, suddenly, my mom gets a text from my aunt saying "I'm at Dad's tree. We should put gardening equipment in the car". Now, Grandpa's memorial tree is about half an hour away from the airport on a good day, so my mother was naturally confused and sent a text to her sister asking when she'd gotten to the tree. My aunt's reply was that she wasn't at Grandpa's tree, and that she had gotten the same text, only it said that it was from my mother!

Mom sent out an email to her other siblings, and two of them have responded saying that they didn't send or receive any texts, and the sibling that hasn't responded yet has no reason to be in Seattle at all. Plus, Mom's phone said the text was from my aunt, and my aunt's said that it was from my mom. Preliminary googling suggests that there's been a couple of similar incidents with Blackberries, but my mom doesn't have a Blackberry. I'm also aware that it's possible to spoof texts and such, but what would be the point of spoofing that particular text?

Any thoughts, internets? Besides visiting Grandpa's tree with gardening equipment, I've already suggested that.