Her behavior is the best “diagnostic tool” you have to determine whether this is upsetting or harming her. Other things to look for other than being clingy or sad would be extreme emotional outbursts, difficulty in being comforted and sleep or eating disturbances. Also, watch her weight carefully. Should she begin to lose weight or fail to gain, this might be an indicator that she is disturbed by the separation. Other types of regression would be important indicators—going back to crawling if she has begun to walk, rejection of solid foods, etc.
Unfortunately there is very little research dealing with longer but regular separations such as your schedule calls for. There is, however, extensive research showing that daily separations followed by happy reunions need not be harmful to infants provided two conditions are met: (1) the baby’s mother is sensitive and responsive to her needs and (2) the supplementary care is high quality. It sounds as though the loving relatives provide the latter, and it is up to you to make certain of the former.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.