This is her own money. But she likely had a gain when she sold the house. If it was her primary residence for two of the past 5 years, she can exclude $250,000 of the gains from taxes. You should see a tax advisor/CPA to find out the specifics of her situation.
If she had a capital gain, it must be reported on her taxes. There may be other forms required because of the international money transfer. Again, consult a tax expert.
The proceeds of the sale should be deposited in a large Mexican bank. I presume — but am not sure — that the transaction is executed in Mexican pesos. In that case, $1 is equivalent to 17 pesos. So divide the pesos you receive by 17 to get the rough dollar amount. Of course there will be fees and exchange rate differentials to get this money changed into dollars and wired back to her bank account. Get wiring instructions from her bank.
If the transaction was made in U.S. dollars, the money can be wired to her bank — but do check that they didn’t rip you off when they exchanged the proceeds into dollars.