While a "ton" of money strikes me as an exaggeration, the YWCA does receive money to help people in need, and this fundraiser is another example of that. The YWCA also has preventive programs; this particular fund-raiser is to help feed those in more dire straits. That in and of itself is a preventive measure, albeit not at the step you're referring to.
Believe me, I am 100% on board with increasing resources for preventive measures at every step in the process prior to homelessness.
This particular fund-raiser is not for those efforts, however, and I suppose I don't understand why you're criticizing the Y for that--this isn't a zero sum game, and efforts are required at every stage for so many people to keep people out of homelessness, and to help those who are homeless to get back on their feet. This is a fund-raiser to help the latter individuals and families, something I'm sure you support.