Joy Morgan, 20, from Hatfield in Hertfordshire, was last seen on 26 December at a church event in Ilford and was reported missing on 7 February.
Prosecutors allege Shohfah-El Israel, a fellow worshipper at the Israel United In Christ church, murdered the midwifery student.
The 40-year-old from Cricklewood denies murder.
Church member Laurine Leach, who changed her name by deed poll to Lydia Israel in keeping with church practice, told Reading Crown Court she spoke to Ms Morgan at the church event on Boxing Day.
She said the midwifery student told her she was unhappy in her student house and had not started an assignment which was due soon.
“She started to cry,” Ms Israel said.
“She didn’t cry for long because I kind of respectfully just didn’t want anybody else to see that she was crying so I kind of dampened it down.”
Another church member who was at the event in Ilford said Ms Morgan seemed “really down”.
Trine Samba, known in the church as Sister Yahzel, told the court: “Throughout the day she was quite isolated. She kept herself to herself.”
Ms Samba said Ms Morgan was not taking part in any games at the event so she asked her what was wrong.
She told the court Ms Morgan asked her: “Do you ever feel ‘what if’?”
Ms Samba said there was then an “awkward silence” but she did not ask Ms Morgan any further questions as she “didn’t want to pry”.
The church member said she was “concerned” when it appeared Ms Morgan had left the church, which the trial heard was “the centrepiece” of Ms Morgan’s life.
The court previously heard Ms Morgan’s phone number was removed from a church social media chat group on 28 December.
Prosecutors allege the accused Mr Israel was “responsible” for removing her number “to cover for her disappearance”.
Ms Israel told the jury the defendant and his wife were like a son and daughter to her.
On Tuesday the court heard the couple had “befriended” Ms Morgan.
After he was arrested, Mr Israel told police he had driven Ms Morgan to her home in Hatfield on 26 December but phone records suggested they were in Cricklewood, where he lived, jurors heard.
First published 10.07.19: https://www.bbc.co.uk/news/uk-england-beds-bucks-herts-48942211