I might just ask her for clarification if she is expecting you to offer some suggestions for her review or if she has told the journal editor that you would be writing the review. If it is the former, then I might just write a few paragraphs for her use if it were in my area of expertise. Sometimes journal editors ask reviewers to recommend other reviewers if they are too busy to complete the task, but it doesn't sound like this is what is happening there.
Thanks..in the end I said something to the effect of “I would appreciate it if you could clarify your request for me to review the manuscript”...I pretended not to know what she wanted me to do so that she would have to spell out in black and white that she wanted me to conduct the review under her name. In the end she claimed that she had intended for me to do the review under my name although we both know that was not her original intention…I think that having to clarify what she wanted made her to think twice about what she was asking me to do.