I am glad that you posted and I am glad to hear from a "child's" perspective. Granted you are no longer a child, but a young woman.
In a way I was like you, my parents did not teach me Mandarin Chinese when I was growing up. I wish they did, but I know that they did the best they could and what they thought was right at the time.
Now I have a 3 year old son who is trilingual as I am teaching him my "native" language, Indonesian, and he goes to a Mandarin Chinese daycare and we both attend weekend Chinese school. We are both learning Mandarin now. We live the USA, so English is the community language and my husband's.
The very best of luck with your Spanish and your life. At least it is great that you have your mother to be your conversation partner and to help you along. Keep up the good work.
modified OPOL - English, Indonesian, Mandarin Chinese.