I was just wondering what people's thoughts/suggestions were on this:

My mom offered to throw us an engagement party. We weren't even thinking of having one. Well, I spoke with her on the phone tonight. I guess my sis asked her (I know, none of her biz) who was paying for it. My mom told me that she told her, "We haven't discussed it, but I 'might' pitch in a little for it. Other than that, I think they are." Well, a few tears of regret later, and I have to tell my mom we cannot have it. This is a tough time of year for us, and we were under the impression that we were having a party thrown for us, not that we were throwing it for ourselves!! Not anymore. I looked up the etiquette on this one, and it said that the parents of the bride were to throw the party. And, if they didn't want to , that whoever else (i.e. groom's fam, sis, etc.) could throw it. What would you gals do? Thanks in advance!!