[Spanish] Create a bilingual children's program to encourage Spanish use

My daughter is three years old and we are trying to raise her bilingual. My wife speaks to her almost exclusively in Spanish and I speak to her in English. The problem is that she understands Spanish perfectly but always responds in English. It doesnt matter if my wife asks her a question in Spanish, she will answer in English. We live in an English speaking country so she gets plenty of English exposure everywhere else. I know she can speak Spanish because I have heard her use words and short phrases with her grandparents when they visit. But day to day she just defaults to English. My wife is getting frustrated because she feels like she is talking to a wall sometimes. We want her to be comfortable in both languages but we dont want to be too forceful and make her resent speaking Spanish. Has anyone else dealt with this? What strategies actually work to encourage a young child to use the minority language at home Should we be strict about