The reason for Miss Linda's 'celebrations' could be easily understood when one learned how loans were given during this time period.
First of all, even the most generous loans of the time usually came with 5 to 10% interest, although the far more common rate was closer to 20%- loan shark amounts.
So compared to that, Alexander's deal was basically interest free.
In fact, the only reason he even charged that small amount had more to do with the principal than any motive for profit.
He just did not want to appear like an endless 'coin well' to Miss Linda.
And secondly, given Alexander had not brought it up, Miss Linda seemed to sense there might not be too much of a repercussion if she was unable to repay the borrowed amount.
Now if a lord refused to pay back his loans, there were a few things that happened, broadly depending on who they borrowed it from.