I understand WT has recently been teaching active JWs that everyone who attends the memorial, are showing they recognize JWs to be the only true religion. By attending, you are supporting their belief that you continue to consider that religion as 'The Truth', even as you do not participate in any other JW activities throughout the year.
JWs commonly attempt to control any relatives who will submit to their methods, crying being one such method. If you give-in, expect similar behaviour whenever there are other JW events labelled as 'Special'.
While my SO and I had attended the memorial for a few years after fading from being active JWs, we finally asked ourselves why we were doing that and creating unneeded anxiety and stress for ourselves by again potentially placing ourselves under influence and accountability to the local elders.
Although many people consider a KH as a church and therefore open to the public, it is in actuality, private property and only accessible by those the elders allow to attend and who will adhere to dress code, behaviour and other 'rules' the WT and local elders designate and decide to enforce. The elders could ask to meet with you as you are attending their facility by your own choice.
Similar to your mother, our JW relatives make an issue of ensuring we know the memorial date and 'demand' that we attend. Early on, they would argue, induce guilt and put on an emotional display both in their pleas to attend and afterwards, when we admitted to not going. Although they now continue to 'request' we attend, it is no longer so emotional. They also do not always inquire afterwards but if they do, usually nothing further is said when we say we didn't attend.
I expect your mother will also soon learn to accept your choices, once you stop giving in to her emotional attempts to control you.
