Thank you for the opportunity to help you with your question!
Think about the two components of her travel distance
1) in cart = +3.3m/s while walking 1.1*t (t=unknown time that we wish to solve)
Then the total distance which can be expressed as the total time(1.1)*ave speed. Equate the two, and solve for t
Please let me know if you need any clarification. I'm always happy to answer your questions.