Sister in law rarely smiles and doesn’t make an effort to converse , spending time with her is becoming difficult?

Sometimes my husband wants to us to go out with his sister. I don’t think she is a bad person. However, if we go out she often sits, rarely smiling. Very occasionally she tries to make conversation with me. I try to keep things upbeat and speak to her but it’s difficult when she doesn’t seem majorly interested. How should I handle this? Should I just keep acting the same way?

Sister in law rarely smiles and doesn’t make an effort to converse , spending time with her is becoming difficult?
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