She is not too old to train, but even saying that, she is a basenji, and no matter the age, a bored basenji will find things to entertain herself, often things we would prefer she not touch. A companion helps, but even so, given temptation a basenji will usually go for it. Think "baby-proof" your house with a baby who can climb, leap, dig and chew. As said above by others, toys which present a challenge will also help.
C