I have two cats (girls) who are amazing. One is very lazy, and the other is a active. So I had some money and bought them a mouse toy that squeaks when it moves. (We have figured out how to make it stop squeaking also.) My active cat won't play with the toy or her sister. Her lazy sister does play with the toy.
My cats were always friends with each other. Why are they not now? These cats won't go near each other since I got the toy mouse.
You don't say how long ago you got the toy. Cats will often get bored of their toys quickly. So, the problem may solve itself. If not, here are a couple things you can try...
Have supervised sessions only. Let your inactive cat play with the toy for short periods of time each day when you are there to supervise. While your inactive cat is playing with the toy, give your active cat a lot of attention. Pet her, and give her a lot of praise. There is something she doesn't like about the toy. After the session is over, give your active cat her favorite treat. By doing this, you are trying to condition her that the toy is not that bad.
Modify #1 by giving your active cat her favorite toy and treat, while you go in a closed room with your inactive cat and let her play with the toy. The toy you give your active cat should be one you only bring out for these special sessions. However, this may not work if your active cat cannot get past the fact that a door in the house is closed.
Get rid of the toy, and try to find another interactive toy. There are many on the market now. This may be your best option. If you are worried about your inactive cat gaining weight, try the interactive food tubes or balls. Below is the picture of the one I use with my slightly-overweight cat. She loves it - she puts her paw in the tubes and gets out the food and it slows her eating.