Hi Lauren and welcome to GoY. I am so sorry your cat was run over at the weekend, it hurts so much. How about Amelanchier canadensis and also A laevis and A.lamarkii.
Buddleia - The Butterfly bush. Quite happy in damp - and shaded - conditions.

Just a few ideas here for you, if you wish you could go for a varigated shrub, the following will do alright in your situation, Heres one to think about, Aucuba, Japonica crotonifolia for me the best of the Aucubas, dark foliage with splashes of deep yellow markings, or maybe Ilex silver queen varigated holly, and another jaw dropper would be Eaeagnus pungens Maculata, these three will give you the interest you need all year round, i have these planted in many shady aspects for my clients truly great plants, but whilst we are on the varigated theme you could chosse Cornus Elegantissima, great foliage and when the leafs fall you will have great red stems through the winter pruning of this shrub results in brighter stem colour, i have one of these just under the canopy of a Yew and with the dark background it real shows up well, varigated euonymous could also be considered.

Thank you both for your suggestions, that's really helpful!! I will do some googling and make a choice from there. Really miss her and will just be nice to have something near by to remind me. Thanks again

a pussy willow tree, they grow easy and like the damp ground.

So sorry to hear about your cat. She will leave a big hole in your life. Hywel, another of our members lost his cat last year. After getting over the initial shock of losing her he was able to offer a good home to another lovely cat.
You do not say how much room you have but you have been given some lovely suggestions. I would suggest Skimmia japonica nymans. It is evergreen, in Spring red buds open as white flowers and it produces tight bunches of red berries which have a tendency to stay on the bush all year so that you may have buds, flowers immature and bright red berries all at the same time. If you enjoy flower arranging it is a good in an arrangement. You should check that although the area is damp it is also free draining or the roots might rot.

So sorry to hear about your cat. I'm not very good at suggesting things but planting something in your cat's memory is a lovely idea and will help.

Its so hard to lose a loved pet. If you want something always bright you may have to forego the flowers as the lovely variegated evergreens people have suggested don't have conspicuous blooms but are cheerful all winter. Could you say how big you want the shrub to be as lots of these grow quite large.