I have been to witness funerals and to "worldly" funerals. I have noticed that at many times that many in the congo do not attend funerals at the KH. I have been to funerals of older ones who have been JWs for years with very few people in attendance and only a few from their own hall. Many have estranged themselves from their relatives I suppose. Funerals at the KH seem like just another meeting and after you have already attended 3 of them for the week that's enough for even the most zealous JW.
Attending a non-JW funeral is not encouraged at all by the Org.--this always disturbed me. I can't imagine not being by my husbands side at the funeral of his non-JW parents. How heartless and cruel that would've been. Somehow the Org translates going to a "worldly" funeral as being a bad witness or a stumbling to others. What a bunch of nonsense.
You are allowed to attend any meeting at the KH, but if you are DFd I would be surprised if anyone speaks to you, which is probably a blessing. You would not invited to attend any get togethers after the meeting. I was told by the elders and others that you could lose your position in the congo as an elder, pioneer etc if you attended any function where a Dfd person was present. The elders in my congo took it a step further and told me that anyone in a position who attended my daughter's wedding could lose their "position." (My daughter was not baptized but living a moral life was marrying a non-JW) They said it could be a "stumbling to those in the community because I was a JW and she while herself was not baptized was marrying a non-JW (her Father was not a JW either)--How twisted is that? Yes, it was a stumbling to the community, but they won't be stumbling into the KH anytime soon as most were shocked by the behaviour of the JWs towards my family.
If you are ever in this situation just do what you feel is the best thing is for you. If you are not comfortable going to the KH you can arrange to have your own memorial or closing ritual for your Mom. Give a eulogy, read a special poem, play some music, hike up a mountain and throw some flowers in the wind--whatever. Invite some people to join you who will be loving and supporting of your process. You don't have to follow the KH rules anymore.