used breast pump? attn nurses/la Leche moms

My sister gave me her medela breast pump that she used for her first baby last year. She did not pump a ton, and she breastfed for 9 months. But for about 3 of those months she had mastitis. Breastfeeding was a bad experience for her!! 
Are there any experts out there who could help me - should I get a new pump (free with insurance) since she had such a bad infection? Do those machines really get clean?