MG, I'm not clear whether by "my songs" you mean songs you have written, or songs which are in your repertoire.

I don't mind the gender being changed, provided it is done in a way which is sympathetic to the original sense of the song. Even if the original composer had a specific person in mind, a singer may well have someone of their own in mind, which gives the song a particular meaning for them.

For composed songs, then it is a matter of courtesy (and I believe copyright law) to get the original composer's permission to make changes. With traditional songs, it is different - there is no "correct" version, and singers throughout the ages have made changes, either deliberately or by accident. In either case, what is important is the integrity of the song.