Temperature shift question- asking for a friend

Good morning!

My best friend recently started TTC and I've been telling her to start tracking her bbt. She started tracking on Monday (her actual ovulation day according to Glow) and woke up and took her temp. She was at 97.4 which was over a .5 shift from the night before. This morning she took it again and it shifted down to 97.1. When I tracked my own cycle (we are on the same "day" ovulation schedule but a few weeks apart) I clearly saw a dip on Monday (97.4) and a rise back up on Tuesday to 98.7. I got pregnant off of that one try so the increase could have attributed to that for me.

Has anyone experienced multiple days of decrease? If so, what could it mean? I know everyone is different and we shouldn't compare, but hoping I can give her some clarity and peace of mind.

Thank you!