A follower had asked me to answer this privately. But, I thought it would helpful if I shared it with others, in case they wanted to make open when letters to their best friends. So here are some of my suggestions:
Open when:

You need to know how much our friendship means - write how much your friendship means you, write some of your inside jokes and stories, tell her that you love her and are so happy that she’s in your life 

You’re feeling sad

You need to laugh

You need some motivation(remind her of her goals and inspirations) — make a pic collage like if she wants to be a doctor find a pic of a female doctor and put her face over it or find pictures of the city she wants to live in, etc 

You’re bored - put a pack of cards, markers for her to draw with, an activity book, her favorite movie on DVD (if she doesn’t have it already)

You’re happy :)


You need a hug

When you miss your bestie - include a photo of the both of you. Maybe buy/make a bracelet or trinket like a keychain that the both of you can always have

For that time of the month… - insert a pad/tampon, make them a period mixtape, insert some of their fav candy

You are stressed out about school/life/etc - include some of their favorite candy, a stress ball, a countdown calendar to something they are looking forward to (a concert, going home, a vacation trip, etc)

You are having a horrible day -insert silly of yourself/anything they find funny

You are going to see me!

You need some a girl talk 

You feel isolated - remind her of all the people that love her and that will always have her back. Write about some good times you’ve shared.

During the holidays - include a festive photo of you two during the holidays or just a photo of her if you don’t have one. Make a card of each holiday and decorate it accordingly 

You are going to a party - tell them to have lots of fun and don’t worry if you don’t know anyone, just go up and talk to them

Someone is bullying you - tell them that they have to be strong and confront this person. They shouldn’t treat her this way and she shouldn’t have someone do this to her. Offer to get a group of people to back her up if they don’t stop bullying her.

You are fighting with your parents 

We are fighting 

You need someone to talk to and I’m not picking up - write that even though I’m not at the phone right now I am always there for you and as soon as I see that you called I will most definitely call you back. 

The first day of school 

The first day from Holiday break
These are my ideas for ‘open when letters’ for your bestie. Feel free to add/suggest your own ideas :)