Albert Barnes on Romans 16:2

That ye receive her, etc. That you acknowledge her as being in the Lord, or as being a servant of the Lord; that is, as a Christian. Comp. Rom 14:3, Php 2:29.

As becometh saints. As it is proper that Christians should treat their brethren.

She hath been a succourer of many. The word used here προστατις) means, properly, a patron, a help, and was applied by the Greeks to one who presided over an assembly; to one who became a patron of others; who aided or defended them in their cause; and especially one who undertook to manage the cause of strangers and foreigners before the courts. It was, therefore, an honourable appellation. Applied to Phebe, it means probably that she had shown great kindness in various ways to the apostle, and to other Christians; probably by receiving them into her house; by administering to the sick, etc. Such persons have a claim on the respect and Christian attentions of others.

(q) "receive her in the Lord" Php 2:29