So far my perspective is that the step sister asked him to go out with her. It has not, to my recollection, been mentioned that the 'friend' ever went the extra mile to set her up. However, as soon as her boyfriend started being problematic; calling the female lead, the 'friend' suddenly took it upon herself to mention a blind date. The 'friend' is insecure. She realizes that her boyfriend has feelings for the female lead, and probably fears that the female lead may take him up on the offer. She sees her as a threat. So to remove the threat, she made it seem like she was concerned about her friend; and wanted her to find love. She also seems like the type who think people can't be happy without being in a relationship.
The guy never approached, nor spoke to her, outside of a possible casual greeting. People may rebuff my statement claiming that he was shy/ reluctant of rejection. However, he approached her just fine in the classroom. This was before she knew she was going to go on a blind date with him. He also knew she did not know it was him; so that bravado of him thinking any mutual feelings exist, due to her accepting the date, would have come out of nowhere. So the ease to how he approached her is not for that reason. He is being overly sweet to win her over. He may be doing this as a favor for the step sister, She may have pleaded for him to do it, he was bored, or he was concerned from an outside perspective that the boyfriend was calling another woman. He may have witnessed it. As seen in text bubbles of the boyfriend calling, others were sometimes around him. His motive may be coming from familial duty or he may have feelings for the step sister.