Portuguese law only prohibits a woman from being a surrogate when she has a working relationship or economic dependency with one or both future parents. Therefore, as long as your sister meets the requirements established to be a surrogate in Portugal (age, state of health, emotional preparation...), there won't be any obstacles.
Read the full article on: Surrogacy in Portugal: Law and Conditions for Foreigners ( 83).
Graduated in Business Administration from the University of Alicante. She has more than 9 years of experience in the field of assisted reproduction and was the creator and director of the first assisted reproduction fair in Spain. She is the director of Wearesurrogacy and is an expert in the sector of surrogacy because during all these years has had the opportunity to know hundreds of real cases of couples who have carried out treatments for surrogacy and the best professionals, international clinics.