Oshi (Uso) no Hittou Majutsushi-sama ga "Oretachi, Ryou Omoi Dattan da ne" to Dekiai Shitekurun desu ga!?

Synopsis

Elna, the youngest daughter of a financially struggling baron, has spent her life fixated on marrying into wealth to cover her younger brother's medical expenses. For that reason, she didn't want to stand out from her surroundings, so she took part in the "fan club" culture that was booming in high society, pretending to support Slenn. However, she is suddenly proposed to by Slenn himself!? And to make matters worse, Slenn seems to have known from the start that Elna didn't actually have feelings for him... (Source: Comic Brise, translated)