How did Binchou-tan's grandmother die?

Question

It seems like it may have been hinted at in one of the flashbacks (there were a few of them in the last episode) and it always seemed like it had something to do with that tree that Binchou-tan's always looking at (and writes a letter at the end).

Did her grandmother die at the tree? Did she die of old age or was it sudden (like getting attacked by a wolf)? It seems weird that she'd abandon Binchou-tan in the middle of the woods if she knew she was dying.

Answer 1

This is explained in the last (4th) volume of the manga:

She collapsed and passed away at a market when she went to a town.

---

The respective page:

^{Image taken from livedoor, a Japanese blog}

Translation:

2nd - 4th panel: Good afternoon. You're Binchou-tan, right? I'm a spokesperson from town hall... your grandmother passed away in the town. Yesterday at the market, she collapsed, and...