A few thoughts to consider:

1. I don't know what any ethics code is for vets. For attorneys, there are limits to what can be accepted as gifts from clients.

2. When I was working in banking, we had strict policies on what we could accept as gifts from clients and what we had to decline.* Now she is working for herself, but she has to set some limits, set some guidelines, for herself and for her soon to be staff. Perhaps you have gone over them.

* To give you and idea: VP's could not accept anything worth more than $25. Executive VP's could not accept anything more than $35. Lower levels were limited to $20. My point here is, for professions which have limits, they are quite low!

3. While YOU consider this a thank you / best wishes for the new practice, she may worry you expect more in the way of after hours service, pricing breaks, payment arrangements, and so forth. And what she has been able to do in the past may not be on offer in the future if she has start up debt as a part of her new over head.

4. You mentioned Staples. Not every office uses them. There ARE other supply companies, lol. W. B. Mason comes to mind as one of many.

I suggest you graciously accept that for now, this is not something you can do. Send her a lovely card for her opening. Once the office is open, consider one of the other ideas on offer, like lunch for the office one day. But I wouldn't suggest tucking this in the card; she has already made it clear this is beyond some limits she is / or feels obligated to comply with. She is trying to do what she believes is the professional thing. Please try to respect that.

Trying to open a new business is worry enough, lol, don't give her more worries just now! You will have many opportunities in the future to deliver something.