She does not take calcium, and i did recommend this.
Yes, it does. The comma is used to separate two independent clauses joined by a coordinating conjunction. Examples of coordinating conjunctions include and, but, or.
An independent clause is one that can stand alone. Since "she does not take calcium," and "I did recommend this" both have a subject and predicate, they are independent clauses.
In this instance, a comma would be appropriate between the two clauses.