Random resentment

Sometimes I remember certain times my elder sister didnt really defend me. Like one time on a bus a complete stranger basically said how I looked like the older sibling instead of my older sister and he just kept complimenting her and I wouldn't care if she was getting complimented but the fact that the old guy said that to me and she said nothing has always stuck with me. 

Its not like I can whine and cry about it, in the past but I think of it from time to time and let it effect me after marinating. Changed the way I thought of her, not this incident specifically but others as well. Like I can never fully trust her to protect me because she'll always choose herself even if it hurts me. Which makes sense, shes an adult with her own life and im an adult now. But yea.