Retaining information isn't all that important unless you're dealing with a child who is having trouble with math facts/ tables. Even then, helping to develop confidence with numbers would be a priority, instead of underscoring the fact that there's a difficulty there.
For general intellectual development, I'd suggest brain teaser puzzles, logic puzzles, visual puzzles like complex jigsaws, and games you can play together that will help her focus and develop resilience - card games are good for that (gin rummy for example).
If you can afford music lessons and an instrument, that's a superb way to help a child use her brain.
And reading is extremely important. Read to her and have her read to you. There are many great book series that are written for children your DD's age. Avoid comic style books - they are fine to help encourage reading in a reluctant reader or one who has been exposed to Wham! Bam! Flash! style of garbage known as "children's TV," but they don't expose children to sustained train of thought in written form and teach nothing of descriptive prose.
For developing resilience and general confidence, have your DD do chores around the house, including her own laundry and some basic cooking (including cleaning up afterwards with you cheerfully encouraging and helping her efforts).