What an unnecessary thing to say to your partner who has sight and intellect. When you see an attractive woman while with your partner, do not try to put her at ease with comparisons. She sees the woman. She sees her attractiveness. If another woman's appearance makes it into the conversation, don't take the comparison route. It's ineffective, and frankly, it's annoying.
A woman who is secure in herself can recognize and acknowledge the beauty another woman possess without feeling intimidated. The woman who knows who she is and what she brings to the table is not afraid of her well-built foundation being rocked by something as superficial as beauty. She's not oblivious, and she can handle the fact that she's not the only pretty woman in this world.
Hear me. The woman who has yet to recognize how valuable, powerful, intelligent, and beautiful she is won't be validated by comparisons. They don't help, and often they magnify self-doubt. In her moments of insecurity, don't tell her about any other person. Speak to her in love and remind her of the things that make her the fearfully and wonderfully made woman that she is.