Friendship breakup (need help)

Well, We (17f and 17f) were best friends since 11 years. Our whole family knows about us. We are in different cities since 4 years. Basically long distance. The matter is 6-7 months back I found something that literally gave me severe trust issues and felt betrayed.(I can't say the reason to either of our families) We were so close like we used to talk 24/7. Waking up with each other's call and sleep after taking to each other. Used to share every second of our life with each other. But that incident made me make the distance and it reached to a point where I stopped talking to her for 4 months straight and as our family started asking questions we started acting like we're just focused on studies. But since Feb we're talking and helping each other in academics as the boards are going on. Today is her MOTHER'S BIRTHDAY and I forgot to wish her and haven't wished till now. She has taunted both of us earlier in call and had asked me many times in a disappointed and irritated tone. It's more like anger. I'm just so scared to wish her rn. What should I do??