Simulating accelerometer in proteus
No, There is no accelerometer library for proteus and there is no way to simulate it also. 

But if you are just trying to check if your code is working before an an actual implementation, you can do that by just taking 3 'Torch LDRs' (a controllable library for LDRs in proteus), One acting  and connect them to a microcontroller's ADC and simulate it. This will just give you an idea if your codes working or not and then you could try some real life implementation

Hope this solves your problem. If you have any other issues just comment!