Legal Question in Civil Rights Law in Pennsylvania

No. The law in PA is that the donor (your brother) made a conditional gift if this was an engagement ring. If they had a fight and broke off the engage,ment, then he gets tpo keep the ring. Since he had possession of it, I am assuming this was the case. If this was not an engagement ring but an outright gift, that may be different - a gift is a gift - it would be her ring.

Since I do not know the circumstances, I cannot advise you specifically. However, I would take the position that this is an engagement ring and that the girlfriend is not entitled to it unless you have evidence to the contrary besides just what the girlfriend says.