Seeking Clarity, I first wanted to say how sorry I am for the loss of your dear mom. I have had a lot of loss, (2 children) myself. I read your mom's experience and have the following thoughts.
I noticed how she had this experience about 3 years prior to her death. It would appear that this was a preparation for her departure from here. My son knew he was going to pass, and so did I.
This knowlege came in the form of dreams, a telepathic voice telling me,orbs showing up in his videos and then, his final notice that came 3 days before his passing. The day he passed, I received a text message on my phone. It was not attached to any phone number and the message was where the contact name or saved phone number would have been. So, I believe your mom's dream -- or what sounds like an OBE event --was her preparation.
2) I was very much touched that she got to see your brother. (her son). I am sorry for the sibling loss, my daughter struggles with that very much. It does show we continue on, and that they -- once they leave here-- are able to recognize one another and express that love.
3) The other intelligent life forms, I think there is so much about our universe we just do not know. My great grandmother's first cousin is Astronaut Deke Slayton and he said that there other intelligent life forms. He encountered on during his astronaut days. Also, his colleague, Edgar Mitchell, also said this about other life forms. Here is an interview from Deke,
https://www.youtube.com/watch?v=4E_SFwrh8wo
I thought your mom's experience was unique in that it tied those 2 aspects together -- both mysticism -- and future/modern technology tie such as the space travel vehicle.
One final thought. Personally, I have found the Gregorian Chants from Medieval times to be of soothing quality to me and feel that the ancient ways have kernels of truth embedded in them. That is why so many older spiritual practices of religions included meditations, chanting, and contemplation. Sadly, so much of this has been striped away.
I hope some of this helps and take your time in the grief journey. Let no one rush you, as it is a unique and individual process.