Would you write a letter to this girl in this situation?

Me and this girl talked for every month for almost 3 months. She has a boyfriend but there relationship was not good at all (I was being extremely respectful about this). I asked her for coffee and she stopped taking to me and acted extremely weird. It's been two months now we have not spoken and my best friend actually confronted her about her actions. She said some things but said she was going through a very rough time with her boyfriend and he monitors her phone and that's why she could not text me. She was looking down the whole time he said. Would writing a letter be appropriate and give it to her through my friend or leave it on her car or is it too late now?

Would you write a letter to this girl in this situation?
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