Responses
I'm not an expert, I don't have any chest tattoos yet, but a tank top would be better just because she wanted it pretty far over on her chest so she'd have to unbutton a fair amount, if not all the way. With a tank she could just put the strap for it and her bra under her armpit and feel a little awkward but still be mostly dressed. That's what I would do, the less you have to undress the better. Especially in front of the guy you're totally still in love with but feeling conflicted about.
Her outfit for getting a tattoo on her chest is not amazingly well thought out, just from this glimpse