When someone has lost their mom, it's important to acknowledge their loss with sincere and comforting words like "I'm so sorry for your loss" or "I can't imagine what you're going through, but I'm here to support you." Offering your presence, a listening ear, and practical help can be very meaningful. Avoid clichés such as "they're in a better place," and instead focus on showing empathy, sharing memories if appropriate, and letting them know they are not alone during this difficult time.