Remind her of her own words : She said she enjoyed your e-mails, ....Tell her how much you enjoy reading her emails too ,because you need family connection since your Fathers passing .
She was concerned that you didn't love Jehovah anymore and that you were reading apostate material on the net ......you may want to ignore this point or ask her WHY she wants to bring this up ? , .... and she said that would be a dividing point for the two of you. Reassure her that this does not have to be a dividing matter among loved ones,family .You respect her religious position ,and all you want is her to respect your privacy . Tell her you have no desire to sway her beliefs ,and that you assume as your Mother that she wants you to be happy too, no matter if that means you choose different ways to acheive that goal . Family should be a bound worth preserving . Bring up another example of how you may not have the same likes in some other matter ,but that does not mean you can not treat each other as family .
Or you could handle it this way : She wanted to know if you were still reading apostate material ,and to be truthful and write her back... I would ignore that request . I assume you are an adult ,and that means there are some questions you just don't have to answer . You could say something along the line of :Mom ,I love you and sometimes there has to be boundries among adults . I feel like you are trying to bring up a problem just so you have an excuse not to speak with me any longer ,Is this what you are trying to do Mom ?
Ask her ,if in the interest of your small family, you can both agree not to discuss religious matters ,but rather have a normal Mother /daughter relationship .So many wonderful things each of you can share about yur lives without getting religion into it .
I assume her conscience is pricking her ,because the Watchtower advice is telling her the correct way to bring you back into the fold is to completely shun you . This belief is based on the reasoning that you will want your Mothers love so much you will be moved to return to Jehovah . Which we all know is emotional blackmail ,but somehow is justifiable to JWs .
I wish you the best of luck on your return email . Please let us know how it turns out . Wishing you much strength !