Thank you.
If you check out
Timeline I tend to put all the supporting info for these things there.
Two parts to my answer though.
1. The text to Desi Myers is reported in Behind The Door (p58). I do query whether this is a UDT time but later on the book states that the last WhatsApp that day is timed at 21:13, so the time is
probably right. Note that Cecil Myers reports this message as being at 22:00-22:30 and gives a loose wording of it. The reason I'm not certain about the 21:13 time is because the last message may refer to the last message to Sam Greyvenstein rather than the last message ever. OP may be referring to this message in his testimony about being with Justin Divaris that afternoon.
2. I think the WhatsApp sent to a friend that afternoon may refer to the reply sent to Gina Myers after she let Reeva know she'd finished at 14:00 and Reeva let her know she was still in Pretoria. I give links to the interview in Timeline.