“Do you wish your prayer to fly toward God?
Give it two wings: fasting and almsgiving.” —Saint Augustine
It is somewhat unfortunate that we Catholics are so aware of what is and is not a sin that we sometimes neglect what the Jews call “a mitzvah,” or a meritorious righteous act. It is not that we lack the concept; for us, such acts would include corporal and spiritual works of mercy, though. In the not-so-distant old days, this fell in the category of fasting and almsgiving, but those concepts are unfortunately not in vogue as they once were.
Consider that spending time with your mother doing things to please her and make her feel loved rather than doing things you would rather do for your own pleasure is an opportunity for you to practice self-denial and charity. Seen that way, it is both fasting (denying yourself pleasures for the sake of self-mastery and the greater good) and almsgiving (giving to others out of mercy.)
We are still supposed to perform acts of penance and almsgiving on Fridays, even though abstinence from meat is not one of the required modes of observing each week’s “little Lent.” You might consider setting time aside every Friday to spend with your mom, doing things she likes, as an act of gratitude towards her and as an act of self-denial for yourself in recognition of the Lord’s Passion. That’s a pretty light penance, when you think about it, but it is far better to give what is most needed than what hurts us the most.