Is this florist illegal/immoral?

I found my florist through my fiance’s sister when she got married. She had her bouquets and boutonnieres through this florist at Kroger for a really good deal. For the past several months now we’ve been talking about designs, flowers, mock-up, quotes, etc. and worked with me in my budget. She was very passionate about it and I liked working with her. When I asked how payment would be made or if there was a contract to be signed she said payment would be made to her so she can get me a really good deal instead of Kroger’s price. Which would be $350 in difference… my fiance’s sister paid her flowers through Kroger though.

That’s when I felt uncomfortable so I created a contract that she agreed she’d sign, I haven’t given it yet. My parents found out and they think that I shouldn’t go to her because it’s not Kroger and they said it was stealing since she’s basically taking the business. I’m this far out and I’m afraid it might be too late to find a new florist. The lady told me I can go through Kroger, up to me but they don’t do signed contracts there anyhow. She buys directly from the wholesaler so even if she weren’t at Kroger she can still get supplies through them.

I mean, is it really any different than say a make-up lady at Macy’s or someone on Thumbtack? Argh. I thought I had this figured out but my parents are making me nervous now about moving forward. Should I just spend extra money for another flower shop?