Now, I am not someone that can read all posts, so I must have missed this along the way about Laura, being alive, and being your therapist, but, I think this was a good thing that I did miss it. I am not sure if it has enlightened you a bit. What I am talking about is, it might be that you 'are' grieving the loss of your grandad, but you could be directing it towards Laura.
I think it is something you may need to analyse a bit yourself. You are also worried about your dad.
You may have had a good relationship with Laura, and it is always difficult to finish therapy and this also depends on how it was finished too and would have been difficult at a time you have had loss, and also potential loss of close family members. So, this grief you are feeling could be an extension to the passing of your grandad. Have a look at this possibility.
The mind does try to protect itself and so might direct it towards a different way of grieving. Still releasing the emotions you need to, but kind of protecting itself a bit (just a thought).
Any loss is hard though. Grieving is also needed for other losses, such as a job, or health, or lifestyle. Losing a home may also trigger grief, so a process and the stages may still be needed in any sudden changes to what someone saw as normality and so would need to go through the grief stages.
Really have a look at this. What you need to be aware of though this is you going through the grief stages, so, whatever you feel about it and if you do feel it is solely about Laura, you still need to go through the stages.
I hope I have helped a bit. I really hope that things do settle for you. Don't carry out any plans to take your own life. You have a lot of discovering to do and I think, once you have gone through the grief process, you will see a way forward.