Can my sister and I be from the same father if we have a different blood type?

This is safe. We can deduce from your data that one of the parents must have blood group A and one of the parents must have blood group O. Furthermore, your father or mother or both must be Rh positive.

The rhesus factor is dominant. The blood group (A, B, O) is referred to as codominance. A and B are dominant over O.

There is a difference between a phenotype, which you mention, and a genotype.
A characteristic that is expressed (= phenotype) is linked to the genotype (which is in the genes).
A genotype always contains two alleles (unless it concerns genes located on X and Y chromosomes).
One sister with blood group A- (= phenotype, which is expressed) has a genotype (which genes): A.-.
The dots indicate that this is an uncertain allele (here it can be the A or O allele).
The other sister has phenotype: O+ and genotype: OO+.
The parents then have a phenotype A genotype AO-. (the . can be a + or – here) and unknown phenotype with genotype O.+. (one . can be A,B or O the other . can be a + or – here). Without blood group determination you can therefore not say with certainty what the genotype of the parents is.
Conclusion: this is perfectly possible.

Regards,