I'm so sorry that you lost your mother in your late teenage years; a crucial time. I had a friend that experienced something similar.
It is so understandable how, when you remember leaning on her for advice, that it upsets you. Your awareness of how your grief then gets passed on to daily events, was so precise, to how my grief works.
Rather than trying to separate out, or get rid of the sadness that you experience, for the sake of your mental health (burying feelings caused me years of insomnia), I'd recommend to work gently with a therapist to understand and process this layer of grief that you are having. If you do it that way, the feelings that upset you will most likely diminish, over time.
I can understand the anger that you experience, if you hear someone criticize her. My cousin was a protector of his mother and I remember feeling him flinch when I suggested to him that his mother wasn't perfect--to help him realize his mother was a lovely person and was a rigid person, and therefore, allowing himself and others to feel anger towards her, was very understandable and very healthy. My cousin later told me that he hadn't yet realized that a person could be angry at their mother and still love them. Allowing himself to feel anger decreased his depression and helped him be less rigid (thank goodness for me).
Regarding progress though this layer of grief, be patient if you can. There may be a good outcome for you,
When I was dealing with a similar situation of both feeling grief, and feeling angry after my relatives criticized my beloved grandmother, after working it through in therapy some changes occurred. I felt her love ground me in moments of decision making. I still talk to her, in my head, or aloud-if no one is around: "What do you think?" And I could also handle people expressing anger about her, as well.
Best to you! :hug: