My little girl kitty wont come down from her tower (ever)

I adopted a sweet little cat years ago and she lived with me and 2 other cats. I purchased a very tall cat tower years ago which she has now exiled herself to.  I adopted another cat about 5 years ago, and she hates him.  she tolerated the other boys didn't have a problem with them.  well I lost one of my boys this year to cancer so I adopted another kitten and also saved another kitten from some evil children.  so ive reconstructed this tower so the top is like a huge living area and also built shelves around the ceiling so she can move around since she wont come down.  I had to build her a bathroom underneath her platform because she couldn't get down to use litterbox.  she would go to bathroom on her bedding.  if I brought her down she would be ok but if a cat scared her she pees all over me before running back up tower.  so I have 5 kitties total and there all boys and she hates when they invade her space wich they love to do.  any suggestions.  have I enabled this to happen by building her a permanent refuge atop that tower. 

When you brought the new kitties into your home, did you do cat to cat introductions or did you just set them free and hope for the best?  Cat to cat introductions are necessary.  They take time, but they allow the cats to adjust to one another slowly.  Cats are territorial creatures and it takes them a long time to adjust to other cats.  They also need to work out the hierarchy system between them.

You have enabled her to stay up there by providing her with everything she needs.  She has no reason to come down.  Do you feed her up there too?  I would start by trying to feed her elsewhere so she is forced to come down.  Start by putting all of the other cats away so she will feel safe.  You might want to have a good play session with her.  Playing with a cat builds self confidence.  Try a da bird wand toy or other wand toy or a laser pointer.  Really get her moving.  It's part of a theory called hunt, catch, kill, eat, groom, sleep.  You play with her for the hunt, catch, kill phase.  Next you feed her a meal or snack for the eat part.  She will then groom herself and take  a nap. 

Here is a video on cat to cat intros.  You might want to start feeding the cats on either side of a closed door.  You may have to start way back to begin.  Eating with other cats is a confidence builder too.  Yet it may take lots and lots of time.  Start with a closed door.  Then you can move to putting a baby gate in the door and covering it with a sheet.  You can gradually lift the sheet up.  This process could take weeks to months.  Try your best not to rush it.  You want the cats on either side to be calm, with no growling, hissisng, yowling or posturing.  You also want the cats to eat. 

i didn't really give them any intro time. the older kitten hes feisty likes to fly all over the house.  he likes being up there she hates any interaction even with the older cats.  I have so many tall towers in the house but they seem to want to invade hers.  I can try feeding her on the ground again.  she used to come down to visit every day when im on the couch but every time she makes a move to go back up the tower the cat she hates chases her up the tree.  I will try the play time thing.  I did make the extra bedroom up for her to be in and have some alone time away from other cats but all she does is cry and the second door is open she makes a bee line for the front room and her tower and she gets chased up the tower.  thanks for input

yes I do feed her up there too.