Thank you for writing in to Just Answer.
From what you describe it sounds like you've made excellent progress with your therapist. You sound very self-aware of the issue you're dealing with and that's a clear sign of progress.
I understand where you are coming from. You are worried that you could be sucked into the same patterns that you've been working to get out of, now that your grandmother has passed away.
Since you are going to be away from therapy sessions I'd encourage you to develop a plan for yourself. This goal plan to so speak needs to contain the possible manipulative behaviors that your mother might engage in and how you will address them. For example, the behavior could be - calling consistently or making you feel guilty and how you will address it could be: "listening to her but staying aware of what she is doing and choosing not to fall in the trap of feeling guilty.".
In this way - a goal plan will help you stay conscious and alert as to the behaviors that your mother might engage in to pull you back into an enmeshed relationship.
A very effective technique to help you stay conscious and aware is called mindfulness. You might have already heard about it but if you haven't here is an introductory CD
that provides lots of consciousness raising techniques to help you get started.
I hope this was helpful.
Please do let me know if you have questions/thoughts to what I wrote above.