From being in the same situation this is the best advice I can give you.
1: At least one long phone conversation per week to keep her interested and invested (she needs to hear your voice, it will let her remember the feelings she had which made her agree to long distance in the first place) Obviously calibrate to the situation but long term it's impossible to do more than this otherwise it gets in the way of other things in your life at the most important times..
2. Emotional spikes are key, send her screenshots of old conversations where you felt your connection together, old photos of you and her together, carefully drop in how you were 'thinking about that time you first met' or the first time you had sex.. it will make her feel close to you again.
1: At least one long phone conversation per week to keep her interested and invested (she needs to hear your voice, it will let her remember the feelings she had which made her agree to long distance in the first place) Obviously calibrate to the situation but long term it's impossible to do more than this otherwise it gets in the way of other things in your life at the most important times..
2. Emotional spikes are key, send her screenshots of old conversations where you felt your connection together, old photos of you and her together, carefully drop in how you were 'thinking about that time you first met' or the first time you had sex.. it will make her feel close to you again.