One of two new books about a bumbling, irrepressible young hippo whose cheerful goal is to help. Here, noticing ""a poor little monkey stuck in a tree,"" she leaps from her wallow and barges off to get him down, equally oblivious to advice, to the hapless other animals in her path, and to the true nature of monkeys -- and hippos. Not until she has climbed the tree (""like a little monkey...oh!"") does it dawn on Betty that she's the one who now needs help; she doesn't know how to get down. However, the resilient palm (rather unrealistically) flips her back to her wallow, to the comic consternation of several wading flamingoes. Morgan's text bounces right along, propelled by colorful verbs detailing Betty's insouciant progress. A frog she accidentally saves en route adds interest to both the plot and the gleeful, meticulously rendered art; he shows up again as a bemused bystander in Helpful Betty Solves a Mystery (ISBN: 0-87614-832-1). Unusually entertaining fare for beginning readers.