<human>: Provide a brief overview of the text.

My girlfriend left me ~2 months ago due to a lot of fighting.  A few weeks after we broke up she wanted to try friends with benefits.  I felt uncomfortable with being fwb's (especially because she began treating me poorly during this time).  I sent her a very long text saying I did not feel comfortable with any type of friendship/relationship until she stopped treating me like shit, and we haven't contacted each other since.  

A week later (today) her best friend texted me saying my ex's sister unexpectedly passed away and that my ex wanted space to herself.  I'm going to respect that wish, she does not need to deal with me right now.  Unfortunately, I cannot attend her sister's funeral because I am leaving for college in two days.  I want to send some kind of text/letter to my ex and her other sister [20], as I was close to them.  I know I am no longer in their lives, but I feel it is the right thing to do for her family.  I'll admit, I still love my ex and miss her a lot, but I don't want to "capitalize" on this tragedy as a chance to try and win her back, that's just awful.  I want to maturely send some sort of letter to them both, but I am not entirely sure what I should include/mention in the said letters.  Does anyone have advice for a situation like this?  Are there any clear do's/don'ts for what I should write?
<bot>: My ex's older sister just passed away and I want to send a mature and appropriate letter expressing my condolences, just not sure what to put in it.