Verbalizing isn't for everyone, and it's better to be clear in a letter than confused and jumbled out loud.
People can, and do, use letters to communicate difficult issues throughout their entire relationship. It works for them, so just because your preferred method is the spoken word, doesn't mean it's the only effective method.
Gralson: my husband (works out of town).
Auto: my girlfriend (lives with her husband Zoffee).
The most dangerous phrase in the English language is "we've always done it this way."