got horses from owner who could not feed them anymore, now she wants to have them bac

Zimbabwe
a lady asked us to take two of her horses because she has 6 horses and could not
feed all of them anymore. My husband and me agreed, because we have got a 49 acre property and my husband used to own horses and has good knowlege about keeping them.

We build stables for the horses, fenced in paddocks. since there are very poor medical conditions here in Zimbabwe, I had to get all vaccinations and other medication and dips flewn in from Germany, which did cost me something above 2000 €.

The horses are with us since February this year.

They do not like to stay in the stables and are happy to roam around free. Although they like to roll in dust and dirt. One of the horses she wanted to put down before she gave it to us, because it was very nervous and is blind on one eye, so it injured itself very often.
Since it is here with us it is relaxed and calm and never injured itself again.

Now she wants to take them back, because she accuses us of not grooming them.

Has she got the right to take them away? Or, can we ask her to reimburse/compensate for our costs we had, before she can take them away?

this is a difficult question to sort out