Have you asked or discussed your specific concerns and/or questions with the doctors who are currently treating your mother? Have you told them you would like another opinion?
I am sure they will welcome any questions you have and if they don't know the answer will certainly find the answer.
I would not let the lack of insurance coverage prevent me from getting a second opinion. Yes it will probably be costly but, if you really think it necessary then get one. I did and I found a way to come up with the money and it saved my life. I realize Canada is different than the U.S. but we still don't always have access to additional opinions or tests without paying.
Cheers,
Mike