Both are correct, but there are limited use cases for -abus. The chief form used across all authors for all words ends in -is, as in anima, animis (fem. dat/abl. pl.).
The only two general exceptions are dea and filia, which regularly use the form deabus and filiabus, and were created (Sihler § 265.3.b) to distinguish them from their masculine counterparts of deus and filius. Words like animabus are comparatively rare (and in the example of animabus, are almost wholly confined to a single late Latin author). Famulabus doesn't appear at all; it is always famulis.
Thus Allen and Greenough summarize it thus:
But, except when the two sexes are mentioned together (as in formulas, documents, etc.), the form in -īs is preferred in all but dea and fīlia.