Would your SO be more comfortable doing group type activities with this woman, to build the trust that she isn't going to continue trying to "steal" you? Who knows you may all be able to develop a mutual friendship. At the moment I think planning on meeting alone is just going to make your SO uncomfortable. At the very least if you plan on having a friendship with this woman public events are the way to go.
Everything will be ok in the end. If it's not ok it's not the end.