28y/o female w/pmh hashimoto's thyroiditis. Cbc wnl except elevated segmented neutrophils 73.3 (42.0-71.0) and low lymphocytes 17.8 (24.0-44.) prob?

Probably Not. The number of each kind of WBC you have is in constant flux and changes depending on many different things. There is likely nothing pathological about your numbers and will likely be normal upon recheck.
Not likely. The values that you have listed are close to the normal range. Unless there are signs of infection such as fever, I would obtain another CBC upon follow up.
Not likely. These results are not significantly abnormal, but it would be worth getting a vit B12 level to make sure you do not have B12 deficiency.