Stepdaughter refuses to walk and husband doesn't listen to me.

My stepdaughter will be 3 in November and constantly want to be held. If you put her down to walk, she cries and throws a fit and tries climbing up your legs. My husband constantly picks her up. I tell him "she's gonna have to learn to walk. Don't pick her up. Let her cry." And he gets mad when I say that. But she's too big to NEVER have her feet touch the ground. She is 30 pounds. She needs to walk. My husband said "she'll walk when she wants to walk." No, she won't. If she gets carried constantly, she will never walk.  We only get her once during the week for a few hours and every other weekend. Her mom constantly carries her and all the good habits we try to enforce go away when she goes back to her mom. We don't give her a paci and her mom does. We help her use the potty and her mom doesn't. It's frustrating. How can we get her to walk? Especially when my husband won't listen to me. I'm like "she is okay to walk. She is okay to cry. She has to learn she can't be carried." 
Edit: She can walk perfectly fine, even runs through the house sometimes. We take her to the park almost every time we see her and put her down and she just throws a fit. She won't walk. She is terrified of being around other kids. She cries and wants to be held if she sees another adult or child. Her mom never takes her to the park or let's her interact with kids because they don't leave the house. She's horrific to coparent with and doesn't speak a word at drop offs half the time because she used to cuss me out at drop
Offs until we took her back to court. She's just awful. The judge called her out on some questionable things like keeping her up till 2 am and sleeping till noon and everything.