1. what elso did he tell your daughter beside what you mentioned above, like did he ask her to go to see him. Really he should come to your house to appologize in person to your daughter, rather than over the phone.
2. what is the purpose of her trip?
3. Does she (your daughter) still like him? Does she see any future potential between them? If no (less than 50%, let's say), don't go. This is very simple, be rational.
Anyway, since she is going. When she's back, ask her how's everything, how did she feel, what did she learn, what else would she do if she chose not going. Thank her for sharing, appraise her kindness. In the meantime, remind her what purpose of our life should be, should we focus on something more meaningful.