Hi trier1960,
Welcome to Apple Support Communities! We're glad you've reached out for help with this. We certainly don't want your mom missing any of your messages.
This would be a setting on her device. It may be that she doesn't have a text tone sound set up for you, or that your message conversation is muted.
Your mom can verify the text tone that is set up for you directly in your contact information. Here's a guide to help. You'll want to refer to the section titled, "Assign a different ringtone to a contact":
Change message notifications on iPhone - Apple Support
If your contact entry has a text tone sound configured, she'll want to follow the instructions in the bottom section of the guide titled, "Mute notifications for a conversation" to verify that your conversation itself isn't muted in the Messages app.
Let us know if this helps, or if you've got any questions.
Have a great day!