perhaps she just needs a companion, although getting another cat can be a difficult thing, as it takes them a looong time to accommodate with each other and a lot of hissing, which may drive you nuts.
Besides, as they grow older cats play less. Each one has a different personality, however, some cotinue to play until they are quite old, others sort of stop after "teen-agehood". When they stop playing they compensate by becoming more affectionate, so over all, it's not that bad. I think your cat is in the transition period between being a child and becoming a grown up and this age comes with its issues, indecissions and of course getting easily bored with stuff.