When I first played ME1 with Molly, I talked to Kaidan and listened to his blah blah blah and, while I found his history interesting, I hated that my simply listening to him equated to flirting, despite not picking the obvious romance options. I was very intent on sacrificing Kaidan on VIrmire.
One of the reasons for creating Tarisa was that I suddenly became interested in Kaidan and wanted to play out the romance. I wanted to give him a chance. Initially, my bias was still there, but I quickly softened to him and Tarisa has stayed true, though it hurt her deeply to have him turn his back on her on Horizon. Fortunately, he sent that email shortly after, and she kept it close and successfully resisted Garrus’ calibrations and Thane’s “siha”ing. I started up Tarisa’s ME3 runthrough JUST to get to her reunion with Kaidan, after watching Molly’s reunion with Ashley. I loved every moment of their discussions on Mars, especially her requesting his trust.
Molly romanced Liara, initially. They shared the connection with the Prothean beacon and Molly appreciated the no strings attachment potential, while still having someone to talk to. I loved the Lair of the Shadow Broker option to have Liara visit afterwards. I liked the opportunity for Molly to vent about the massive weight on her shoulders and, in ME3, I appreciate that Liara still serves as a shoulder to lean on for Shepard; someone to talk to. Every girl needs a good girlfriend to confide in. Liara has matured quite nicely.
Molly saw Garrus as something more when she “rescued” Archangel. She supported him on his justice quest in ME1 and in ME2, after initially checking his resolve, backed his decision regarding Sidonis. (In contrast, Tarisa chose to save Garrus from those decisions and would not allow him to kill his targets in cold blood.) Molly recognizes the capable leader within him and encourages him to lose those pesky self confidence issues to ensure that, if she isn’t around to make the tough decisions, he will be able to. She’s got a soft spot for his need to impress her and appreciates his tactical and military advice.