Just because you do not have a signed statement from her acknowledging the loan does not mean that you did not loan her the money.
You should first send her written demand for return of the money. The written demand should be sent by certified mail. The demand should be simple. "On [date] I loaned to you $26,000 for the purchase of your house. Demand is made that you return the money on or before [date]." If the sister-in-law fails to return the money by the date set forth in your demand, you would then have to commence a lawsuit to obtain a judgment for $26,000. With a judgment you would be able to attach assets she may have for the return of the money.
Mike.
