Oh, this makes me so mad and sadly I see it all the time, i'm a trained fine artist, I was a professional photographer for a little bit after uni- I worked bloody hard to get the shots I wanted, the advertising I thought would catch peoples attention and shoots I thought people would be interested (ie new, not your standard shoot) and they were always ripped off but it's the kind of industry where I would expect it. Mostly because everyone who has a camera believes they are a world class photographer! I stopped bothering a long time ago.
I'm so frustrated for you because it sounds like you've worked really hard and obviously what ever you do is great or she wouldn't be so hell bent on copying you. Remember, in the UK whatever you create automatically has copyright. I think my advise would be to approach her about it and tell her how disappointed you are in the fact that she appears to be copying you and all your hard work.
Creatively I genuinely understand the frustration, last year a well known company completely plagiarised the artwork that I had illustrated for my daughter's book, blatantly, I mean I had people messaging me all over the place to ask if we'd seen it and if they'd approached her to use her story. (Think Chris Riddell's issue with the monster under the bed John Lewis advert) My daughter has her own website, she's prevalent on places like twitter, Instagram for what she does, is interested in and we do share her work/ my work (a caption accompanies a picture). It was no mistake and it was pieced together almost scene for scene from the parts that we had shared, I believe that you know how utterly devastating this was to see and all Christmas! We approached the company who had no idea they were so similar, they said it was down to the creative agency they used to create the advert (they had worked with them previously). They denied it of course, said that it was an extension of their previous advertising for the company- it was very different actually.. but they were much bigger than we were and the problem that we would have also faced would have been going through a solicitor/ court and we just couldn't afford to do that despite it being a carbon copy, luckily you are small company and by the sounds of it, she is an amateur 'businesswoman', I reckon contact from yourself and then from a solicitor if she does not take it down might just do the trick. Do let me know how you get on and hopefully, everything will go your way.