No lounge access if you aren't flying with her (that would allow you to guest her in).

You can add her as a family member, but this will only give you 20% of her miles. So unless she won't fly EK again in 3 years, not worth it. Even if that is the case, BLR-JFK on a flex fare will earn her about 13,500 miles. You can easily purchase the difference required for an upgrade. Not cost effective if you plan to use the miles for a Y redemption though.