when you do please let us know what might trigger tasha's new questline event, I'm honestly convinced that it's either bugged or requires the sharing route
I've tried to trigger it with a new save file with 0 progression other than getting the car with no luck, also tried it with a harem route save and still no luck
did a bit of save snooping and found that she has a hate counter (tasha_hates_you number variable) and a flag called "tasha_is_ready", I've tried messing with the values but found no effect.