my bunbun also wanted to borrow money from me (HK$4000) after she working for 5 months.
my bunbun is OK for house work, cooking. but i did not show the "softheart'. i said no and told her that my money is tight, i don't have extra money.....
so your helper may be just try your bottom line. i don't think if you say no she will do something bad to your kid.
you can use the same reason as mine and reject her. your helper will not have hard feeling.