Am I liable for anything regarding the two blankets I bought from my neighbor at a cheap price, knowing that she had not yet paid their price to the original seller after purchasing them in installments?

The woman who sold you the item, which she had bought in installments, was its owner. Therefore, your purchase from her is valid and there is no issue with it. The fact that you bought it from her at a low price, and similarly, the woman's refusal to pay the seller, none of this affects the validity of your ownership of the item, and nothing is incumbent upon you.