Question: The witch made the bear Mor'du, in her shop has a bunch of bear carvings, and also turned Merida's mom in a bear. Did the with mess up the spell and made the bears by accident, or did she change them into bears on purpose?
Answer: The witch seems to have an obsession with bears which makes the more likely scenario that the potion turned them into bears on purpose.
Answer: Elinor tossed the bow into the fire in a fit of anger, then regretted what she did and rescued it.
raywest ★
To add to raywest's answer, she threw it in a fit of rage, yes. As a parent, you sometimes disagree with your children's passions, while you try to steer and guide them, they love what they love. She may have disagreed with Merida having the bow, but she also knew how important it was to her. Its hard to explain, but basically while she objected to Merida having it, she knew it was the one thing that made her happy... she loves her daughter and wants her to be happy. She destroyed it in a fit of rage, and then realised she destroyed, for lack of better words, her daughter's "happiness." Marrying her off was one thing, burning her only joy is another.