Approach her on your belly, eyes half closed, not looking at her.

I adopted a feral cat. Ignored her for about three weeks. One night she peeked over the couch and jumped in my lap. It just takes time.

Good on you. Patience.

Make her a soft bed inside a cardboard box, open on one side. Slowly and gently hand feed her some treats while she's in her bed. Try to pet her a little at a time. She'll come around soon. Good luck.

Good for you for taking a rescue cat. Sometimes they do come with lots of baggage. Be patient with her, she is mourning the loss of her babies, and as others have said decompressing.

Congratulations, and I look forward to seeing your photos of her! What's her name?

She's had at least a couple of upsets in her environment that we know of, and it's hard to say what happened on the streets, so it must be rough on her to wonder what changes are being forced on her now, and what others are to come. I'm sure your patience will be rewarded with the positive reinforcement methods everyone's suggested.

MizJ's suggestion with a bit of catnip rubbed in. Also if you have it a red laser dot flicking around the room from outside may get her curiosity working. Let her know you are the one feeding her. If she likes fish I've found that dried anchovies from the Asian food store are a great tempter with most cats. If not fish dry some chicken breast cut into very small pieces into chicken jerky - 80°C in the oven or air fryer for a couple - three hours should do it or if you're wealthy $40-60 kilo.

Her curiosity will kick in, hard to say when. You could put items of clothing you have worn close to her hiding place so she knows your scent, be careful not to frighten her. The shelter was likely traumatic and she is healing.

It depends on her Age, History and Memories, it's much faster and easier with kittens.
Try to make a logical connection between your presence and her food to her and be patient.
how old is she ?!