Any advice on my daughter (15) meeting her birthmom for the first time?

They have had "my space" contact for about a year and a half - just letters and photos before that. Her birthmom has a strong desire to see her. My daughter was recently informed by her that her birth father had been the victum of a shooting in another state. Understandably my daughter now fears waiting to meet her birthmom and half sisters. At this point I plan on making the trip this weekend but would be grateful for any advice to prepare us all.
Your prayers are also gratefully accepted....

I would just say to be

I would just say to be flexible,  people's expectations can vary. I would say your child's comfort is the number one issue. The adults should take the cues from her.