A woman such as Miss Dashwood would get her pin money from her invested inheritance money. In Elinor's case, that wouldn't be much. However, whtever pinmoney she has wouldalso be taken out of the "pool" that Mrs D and the three girls live on. So Elinor might beneift financially from marrying, but the other Dashwoods would be impoverished furhter, would they not?