According to Hinky, Casey spent the entire day of June 21 at TonE's apartment:
"21/22 – KC is at TL’s apartment all weekend. MKi asks where Caylee is and KC tells her she is at the beach. KC adds 23 photos of her at Fusion to her myspace page.
21 – 9:30 am Anthony home leaves voicemail on KC’s cell.
9:30 am KC calls voicemail.
10:23 am KC calls TL, 20 minute conversation.
10:56 am Anthony home leaves voicemail on KC’s cell.
10:56 am KC calls voicemail.
11:11 am KC calls Anthony home, 1 minute duration.
12:40 pm KC calls AH, 7 minute duration.
4:52 pm Anthony home leaves voicemail on KC’s cell.
4:52 pm KC calls voicemail.
4:53 pm KC calls AH, 2 minute duration.
4:57 pm KC calls Anthony home, 4 minute duration.
5:01 pm KC calls AH, 4 minute duration.
8:19 pm KC calls Anthony home, 1 minute duration.
8:57 pm KC calls TL, 1 minute duration.
10:15 pm TL calls KC, 6 minute duration.
11:32 pm JG calls KC, 3 minute duration.
From ping map produced by Websleuths here for KC’s cell phone activity on 06/21/08, KC appears to have spent the entire day at TL’s apartment."
http://www.thehinkymeter.com/casey-anthony-murder-trial/timeline-and-discovery/
I find it hard to believe that Casey wrote this drivel in her diary while she was at TonE's place and then returned the diary to the Anthony house, where it could be found by Cindy.