Amanda Batula and West Wilson’s messy relationship timeline finally blew wide open during part one of the "Summer House" reunion Tuesday night ... and the Bravo bunch did not hold back on setting the record straight.

The season 10 cast peeled back the curtain to breakdown when sparks first flew between Amanda and West, as the forbidden couple revealed it all was "PG" at first ... until the day the pair dropped their joint statement in March.

As the episode begins, reunion host Andy Cohen is seen in a private moment with Ciara Miller -- who dated West and was best friends with Amanda -- as she reveals she is way more hurt by Amanda's part in the scandalous, friendship-ruining incident that was revealed earlier this year.

Once the bunch was settled on the couch, questions about the timeline of Amanda and West's relationship began to unravel ... Ciara revealing she first became suspicious back on Jan. 17 after Amanda ignored multiple calls and texts while her location showed she was allegedly at West’s apartment.

Things escalated fast when Ciara accused West of dating a woman named Meija Moreno, while secretly pursuing Amanda -- however West denies they were ever exclusive and Amanda reveals she knew he was seeing Meija at the same time.

The pair claimed their first kiss happened in February after brunch and Amanda also insisted they didn’t have sex until after releasing their joint statement confirming the relationship on March 31.

Ciara did not hold back when she suggested Amanda and West actually might work as a couple ... because, according to her, Amanda allegedly won’t challenge him -- adding, "The best woman for West is someone who’s not gonna check him on anything. That’s totally Amanda."

The savage comments visibly crushed Amanda, who broke down in tears while Kyle Cooke -- Amanda's estranged husband, who was seated right beside Ciara -- admitted even he thought the remarks were "harsh" ... however Ciara visibly felt no remorse.

As we previously reported ... West and Amanda are currently galavanting around Rome to attend a family wedding. We obtained video of the two at a romantic dinner Tuesday night, hours before part one of the reunion dropped.