Toddler and newborn pump feeding

Alejandra
I've been feeding my newborn pump milk. She doesn't always finish it. My toddler was weaned at 1 year now she's 1 1/2 she sneaks off with my pump milk and drinks it. Idk if this is ok. She's been doing this for 2 weeks now. She has no interest in breastfeeding but my pump milk she can't stay away from.