why u have to judge

frankly, i don't think the girl or her family told you the truth. 

why didnt they tell you the true reason ? i think it is more related to the family privacy that they won't want to share with you. 

for example, the girl got her period and did not want to play with water, while not wanting others to know she got it so early.  or something similar. 

the bottom line is, their decision did not hurt you in any sense, and what you need to do is to respect their decision. this is the basic interpersonal relationship rule.