Hello and welcome from me, too! I'm afraid I have only a moment to post right now, but I did want to address your medication question. By any chance, do you have any friends or relatives in the U.S.? The reason why I ask is that one option for you to consider might be a "compounded" version of trilostane instead of brand name Vetoryl. Trilostane is the active ingredient in Vetoryl, and there are compounding pharmacies here in the U.S. that can prepare custom doses of trilostane at a price that is typically much less expensive than the cost of Vetoryl. There have been some studies that have indicated that some compounded versions of trilostane are not as consistent in dosage or as effectively metabolized as is Vetoryl. However, many of our members here have used compounded products with success, and if I did not feel as though I could afford the cost of brand name Vetoryl, I personally would opt for a compounded trilostane rather than not treating at all.
I just now checked with a compounding pharmacy located in Arizona that has an extremely good reputation with our members: Diamondback Drugs. The pharmacist there told me that they could, in fact, honor a prescription faxed from a Mexican veterinarian. However, they cannot send the medication across the border themselves. They could, however, send the medication to a designated recipient in the U.S. It would then be up to you to work out the arrangements for receiving the medication yourself. I don't know whether this helps, but I just wanted to offer this option as a possibility. Here is Diamondback's website if you want more information:
http://www.diamondbackdrugs.com/
Once again, welcome, and we look forward to learning more about little Cherry. One thing I'm especially wondering about is her enlarged spleen. That is actually not typical of Cushing's, and I'm wondering what your vet thinks may be the cause of this enlargement, and whether it needs to be investigated further, separate from the Cushing's.
Marianne