what if the companies/brands see that she is selling it on?!
It's not an issue for the brands and an influencer can do as they please with the product.
*I used to work in promotions.
Often brands will send PR just in the hopes that the influencer will show it- so without an explicit agreement that it will be promoted. If the product is not in line with Emma's brand (like these happy floral outfits), she will stow them away and then offload on depop later.
If they do have an agreement for the PR stuff to be showcased, then she is free to do what she likes with it as soon as she's fulfilled the advertorial arrangement (for eg. if she was contracted to show it 3 times on insta, then twice in her YT videos, then once she has done that she can do as she pleases with the item).
It used to be that PR items were loaned out and then returned to the brand once the promotion is completed, but in the past 5 years or so it's just been flat out gifted to the influencers. It's hers now, so she can keep, gift, throw away or resell.
Like others have mentioned, she really should be using the free stuff to generate money for charity, rather than reselling for personal profit. It's the decent thing to do if she has not bought the item with her own money.
Goodness knows the NHS can use all the funding they can get during this pandemic. I find it utterly disgusting how greedy and selfish influencers are in this regard. They have multiple brand deals and many revenue streams so they don't need the money from selling PR items. These sales would do so much good if donated directly to charity.