What more can I do for feral Mama?

Mama is about 2.5 years old. I remember first seeing her as a kitten come by my yard on occasion. In June she brought her 3 appx. 8 week old kittens on my back deck under my grill. A rescue group loaned me two traps and I caught them all over 24 hours. The rescue group set up a TNR appointment for Mama to get vaccines and fixed. I agreed to foster the 3 babies. Mama was ear tipped and I released her back into my yard and have been feeding her and working on gaining her trust. I fell madly in love with the babies and they socialized quickly and my two resident cats (age 1.5 and 15) readily accepted them, so now I have 5 indoor cats! So now there's Mama. She's a talker. Sometimes she answers and comes when I call for her. This summer, I sat outside and talked to her from a distance and we had long conversations at each morning feeding! I have bought her a heated house and set it up on my covered front steps and have transitioned from feeding her in my back yard to the front porch to make it easier on me for the winter. It only took 3 days to train her to come to the front for food and water. I have made several tote/styrofoam/straw shelters I have set up under my deck and in the front bushes where I have seen her run off to. Not sure if she's using any of them though. She will eat in the heated house, but then immediately leaves. I can get her to come within about 5-10 feet of me if we are both outside, but she's very timid. I'll sit on the other side of the glass storm door inside my house when she's on my front steps and talk to her, inches away from me through the glass. Her babies come to the door and windows and they look at each other. My vet said Mama might recognize them as her kittens, might not. I'd love to bring her in, but at the very least want to have her outdoor life as happy and healthy as possible. She looks good. She was 9 lbs at the time of TNR and appears healthy.

We just had 8 inches of snow and I shoveled paths through my yard from the shelters to my front steps and placed food in multiple locations for her, but I have not seen her in over 36 hours. I have been so worried about her. Is there anything any experienced feral caretakers can suggest I do to continue to gain her trust and care for her? There is another cat, one with a collar, who comes around and eats Mama's food. I have no idea to whom it belongs and I have not gotten close enough to be able to read it's tag. But it often scares off Mama. She's always on my mind!

Thanks!!

She's a beautiful cat @SimonSchuster  Thank you for doing so much for her.

Don't worry if she takes off for a few days when it snows. I've noticed that feral cats sometimes do this. I think one of the reasons they disappear is that they find snow disorientating. Cats don't see very well and they rely on their sense of smell to recognise familiar places. When it snows the smells they are used to are hidden. I think cats tend to hunker down in a safe spot and wait until things smell normal again before they venture out.

Keep putting food out for her in the usual places so she will know where to find it when she comes back.

Another thing feral cats like in the winter is if you boil some chicken and leave the hot water out for them. The smell of chicken fat in the water attracts them to it. It's often difficult for feral cats to find anything to drink in the cold weather as water bowls and puddles freeze so quickly.

We've got deep snow here today too. I feel sorry for all those outdoor cats.

Thank you!! I'll boil some chicken today! It's 12 degrees and still no sign of her.

It sounds like she's been provided with quite the spa!  I can't think of anything else you can do (except Norachan's excellent suggestion for warm chicken broth)

The fact that she's talking back to you makes it appears she may have been socialized at some point.  True feral cats have no need to vocalize meows or chirps.  They speak to other cats with body language and the occasional hiss.