my son is 13 months old and we have dairy issues here too. Trying to feed him is so hard, and he has had things I didn't give my older kids till they were school aged. Is canned soup too high in sodium for a baby, yep, it is. Does it fill the tummy, allow good practice eating, provide protein and other nutrients, yep again. I was at a total loss today and made my son a hot dog (all beef, but still) He is not only allergic to a lot of things, but he's picky, and he didn't eat it. But I'm constantly trying to find foods he will eat, that won't make him sick, and that offer some variety, because if I let him he'd live on fruit and cheerios (which by the way are also higher in sodium than a baby needs). Even canned veggies are less than great for a baby because of sodium, but we all have to eat, and when you are already fighting food battles, you do what you need to do. I wouldn't feed it to her every day, but it's not going to hurt her.
and as for the homemade soup, it was probably the texture, canned soup is really mushy.