Geez louise people it's not that difficuy to grasp!!
The money was representative of her nasty past, of her time spent selling her body for money, a time which she is ashamed of and doesn't want to be reminded of anymore. So to cleanse herself of her guilt of it, she throws all her dirty money away, allowing her to start a fresh life with her new love and move on from it. If she relied on that money anymore, whether for food or for gifts or for dates or ANYTHING, then she would still feel the guilt.
If the money was from killing people or mafia and other similar "dirty" jobs like that, then I wouldn't mind her, throwing the money. But since her body got "soiled" by havin' so many sex partners, then I agree with other people, saying that since she worked hard for the money then she should've just keep them. For dire situations or anything.
But ya, manga's like that, it won't change no matter what we do. Everyone has their opinion and basically there's no meaning in it xD Wanted to share, thanks, bye xD