It could be any number of things, from some problem with her signup information, or her payment method, to her not receiving welcome/response emails at her email address (maybe she mis-typed it at signup, or had them end up in her spam filter).
We are only customers here so we can only guess; DreamHost support would have the best/accurate answer(s).
Two things I suggest trying:
Have your client login to the web panel and review her support history - this will include any email from DreamHost that she did not receive in her inbox - by checking there, she may find either a welcome message with credentials, or other contact from support that she didn’t see in her email
In addition to submitting a new support ticket, if she feels they are not being received by DH support for some reason, she could try contacting them via the form at http://dreamhost/com/contact.cgi.