All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, may Allaah make better your solace on the death of your mother and we ask Him to forgive her and have mercy upon her. Also, may Allaah reward you for being keen on being kind to your mother, grandmother and maternal aunt.
Indeed, you did well by advising the daughter of your maternal aunt to take care of your mother after you travelled. As regards the negligence that you feel towards your mother, then this is the feeling of the dutiful people. Verily, a dutiful person feels that he is negligent about the right of his parents no matter the extent of good he does to them. There is no doubt that everyone is negligent about his father or mother as they have a great right on the children. It is confirmed that the Prophet said: “A child can never reward his parent unless he finds him/her as a slave and he buys him/her and then frees him/her.” [Muslim]
Being negligent [towards the parents] is not necessarily being sinful, especially if one has a sound reason. However, you should not have refrained from talking to your mother if there was no sound reason for that, but it appears that you are not sinful as you did not intend to desert her, and you were keeping ties with her by being kind to her.
Finally, we give you glad tidings that in Islam the door of being kind and dutiful to the parents remains open even after their death so that a person who was negligent towards them would make up for his negligence by supplicating for them, seeking the forgiveness of Allaah for them, giving charity on their behalf, being generous and kind to their friends and keeping the ties of kinship which are dependent on them. For more benefit, please refer to Fatwa 83233.
Allaah Knows best.