love the painting in the shower idea!
Firstly, you need to work out why she is bored. I know I wrote my earlier post about the tv, but thats only a small part of it. If she is watching a lot of tv, then you need to work on fixing the bit about why she is watching a lot. If she is not watching a lot (less then 1hr a day) and is still bored and understimulated, then you need to fix that. Fixing it isn't just handing her toys - its a mix of socialisation, variation in activities, different environments. I know you said you can't be the one to play with her all the time, whats all the time? You don't have to write it, its just for you to think about. You don't have to physically play with them or play kids games you can get her involved in activities you might both enjoy. Maybe going out for a babycino in a coffee shop?
To stimulate my kids, I rotate toys, use the element of surprise by either setting up activities or putting out a new toy/book/workbook before they get up.
we do social activities like playgroup, (or homeschool group), go to different playgrounds, swimming lessons, library storytime, visiting relatives/friends houses, hanging out with other kids, kindergym and whatever other opportunities arise.
I change their environment by going to other environments for them to explore like the beach, the forest, botanic gardens, national parks, city.
Mine discovered a couple of days ago that chalk makes great paint. tub of water, piece of chalk, thick paintbrush. draw on something - mine have an old wooden kid table (cement/blackboard would do just as well) let them go for it.
let her cook by giving her different ingredients that are yummy to eat. put them in lots of different bowls and let her go for it.
Instead of putting the tv on, put music on and stick a dress up box out. I was thinking tonight I might get a chest and every day leave a few items in there. (eg hats, feather boa, necklaces, cape etc) but everyday something different.
Toys that I find invaluable are - train set, play kitchen (an old kids table with op shop cookware is brilliant, dress ups, blocks, duplo, puzzles, baby doll and pram, workbooks, barn + farm animals, matchbox cars. My kids don't have heaps of toys - its basically variations of that stuff.
Its changing it around thats the important bit. Kids with heaps of toys play with very few.
I think its important that kids can have space and time to be free to play on their own. Its very difficult with an adult hovering over them or trying to lead their play. Some days I will ask my kids what they want to do and let them lead the day. Sometimes adults need shaking up a little and kids are the ones to do it. eg. I will say what do you want to do and the answer might be "go to the beach" but it might be 15 degrees outside. We will go anyway - pack accordingly and the kids will have a ball. They will then decide its too cold to be at the beach and they would really rather play at the playground across the road. Hot chips might be good for lunch and a walk on the jetty to watch the people fishing sounds like fun too. Hey - beats the housework I had planned!
This can also be done around the home. Just let your kid lead the play or the bushwalk/naturewalk. Its really hard to not try and steer it to what you want to do, but they get so much out of it. They truly love you being there and just participating in their world. Doesn't have to be for long.
Hope that helps a little!