I marry Ysolda in most playthroughs and have never had this problem. The marriage went fine, no glitches, and she moved into Lakeview Manor. I can ask her if the store's made any money and she gives me my share, as normal, but she does not actually have a store which I can use to buy/sell. Any ideas?

Running all DLC at the moment. I tried disabling/enabling her via console but no luck.

Edit: Of course it's always two seconds after I post a help request that I fix the problem. Rather than delete this I'll just let you know what I did in case someone else runs into teh same problem.

She'd been hanging out on the deck since she got to the house. I went inside and waited till evening. When she came in she had the dialog option to ask how the children were, something I couldn't ask her outside. Once I asked her how the kids were the buy/sell option was available.