A sad reason for planting garden - my condolences on your loss - but a living memorial garden is a wonderful idea. Here are some plant posibilities that come to mind...
Trees - either a Redbud (Cercis canadensis) or a Magnolia - maybe a 'Royal Star' (Magnolia etoile 'Royal Star') might be appropriate. There is also a line of magnolias that have people's names - I have a 'Susan' and a 'Randy' magnolia - a bit 'cutsy' but I couldn't resist trees with my husband and my names! Depending on your daughter's name, you might be able to find a magnolia variety with her name on it! Both magnolias and Redbuds flower in pink in early spring before they produce leaves for the year - appropriate for the memory of a child who was lost before she had a chance to 'leaf out'...? A pink flowering crabapple is another possibility. All of these are smallish trees that would suit a smaller garden.
With the tree you could plant shrubs like dwarf Korean Lilac 'Palibin' (lavender-pink flowers in June) or a 'Pink Beauty' Potentilla (blooms non-stop June-October; is late to leaf out; flowers bleach to almost white in the heat but are peachy-pink in cooler weather...) Both those shrubs need lots of sun so plant 6-8 feet from the base of the tree, on the sunny east or south side. 'Little Princess' Spirea is a small, pink flowering shrub that blooms in July that you could use as well - it also needs sun. There is also a June blooming 'Pink Princess' Weigela - another full sun shrub.
For perennials, you could plant things like the fall blooming Japanese Anemones which come in some very nice pinks and can take a fair bit of shade, so could be planted under the trees. For fall color on the sunnier side of the tree, asters and mums would give you lots of pink choices. Bleeding Heart is a nice pink (or white) spring blooming flower for shade. The Dicentra spectabilis types die down after flowering but some of the smaller Dicentra formosa or eximia types do not (unless hit by extreme heat) and may bloom off and on all summer. You could add some Christmas or Lenten Roses for early spring bloom and evergreen foliage - they come on colors from white through pink to deep purple and grow in shade. Forget-me-not seems like an appropriate choice - it is usually blue but there are also pink varieties. It is a biennial but seeds itself around freely so you'll always have it! For summer bloom you could have Coral Bells (Heuchera) which usually have interesting colored leaves as well as flowers. Cranebill - perennial geranium - comes in many shades of pink, blue and white, a wide variety of bloom times and can take a fair bit of shade. Siberian irises in white would be a nice addition with their grassy foliage and pretty flowers. Lupins are summer bloomers and come in some pink shades and, while usually grown in full sun, can take some light shade.
There is lots of choice in plants; you just have to decide how big you want the garden to be and what type of plants appeal to you the most. Blues and whites go well with most pinks as do plants with silvery foliage. An unrelieved pink garden might be too much but, with some white and blue touches, it should all blend nicely. Good Luck.