sophia's a sucker for nipple play.
she's turned on probably from the compliments given to her by her students and her pussy was already damp before she got down on her knees.
the nipple teasing from the 3rd student seems like he did because he wanted to not cause she told him to do so. if this happens and there is a filthy path it may push her to let it happen.
nipple play always makes her lose control of herself before she catches herself in the middle or near end of foreplay and wonders how a married women could ever do this. she'll become increasingly hot and losing control of herself, i feel like the confident student with the bigger cock is going push it in her mouth unrequited. or she may get convinced (put under in the moment pressure) to agree with giving kisses to their cocks before (or doesnt) give them or one a blowjob. she'll catch herself with a reality check when the first string enters her mouth.
seems like a possibility to me