She'd better have a business reason/invitation letter

if she wants to enter again using current B1 visa. Although the odds that she could be refused entry is low, she should be prepared to answer some routine questions related to business in the U.S.
Under no circumstances should she present the border patrol officer an invitation letter from you, while entering with current B1 visa. She will be denied entry because the purpose of her visit doesn't match her B1 visa.