Thanks to the OP for this thread.
I definitely think Willow would have messed with/erased Tara’s memories more than what we saw on BTVS. Tara was so afraid of Willow using stronger and darker magic, as shown in season 5, right before Tara is abducted by Glory. Willow had to resort to strong magic to save Tara’s mind, despite what Tara might have felt. As we know, Tara’s opposition only escalated as Willow’s power grew, and as Willow’s power grew, she needed to control Tara more.
IMO if you go back to season 4, Willow had a taste of the mind altering ability in Something Blue and that is the moment, IMO, that she got hooked on the drug as a means of killing the pain from Oz leaving her, but in Willow’s pathology, it was all about the addiction, then the power that came from it, fuelled by more addiction to kill pain, and so on. So earlier than the Glory Days.
if it is possible to show how Willow regretted the multitude of times she either erased memories or altered them, perhaps her profound guilt and reluctance to use her powers in season 7 is evidence. In Conversations with Dead People, Cassie is able to manipulate Willows guilt so effectively, that it makes me wonder, Willow isn’t only grieving Tara’s death, she is deeply regretful for abusing her.
One of the overarching themes, IMO of season 7 is forgiveness. Without that, Willow is unable to continue with Kennedy and begin using magic safely again. For that she has to forgive herself for the unspeakable harm she inflicted on Tara.