"The amount of alleles that a baby Guinea pig inherit from the mother are two , 1 from its mother and 1 from its father.
ie: if its mother had a dominant black fur (BB) and its father has recessive grey fur (bb) , there is 100% chance that the baby will has a Bb genotype, which will give them either black fur or dark grey fur."
Yes, the mother likely has several dominant alleles that manifested as a heterozygous genotype in the baby, giving it a phenotype largely similar to its mother.