Is it in California? Some states have market value taxes, but here in prop 13 land, it’s pretty cut and dry, sales price is the law of the land.
There can also be things she isn’t telling you or she may not understand some of it. If you buy a trainwreck foreclosure and need to pull permits to repair or add things, the addition is added to the sales price to determine taxes, but I’m doubting that is the case since it is a condo.
Most of us in so cal have been reporting the opposite, where they are lowering taxes without even asking. You can look up her taxes using the address online, most counties have an online system, check it.
My last guess is that she will get a refund, I bought my place at the end of 2008, had to pay the taxes for the remainder of the cycle based on the former assesment, which was double. They just got around to updating it and are sending me a refund for those six months. Same thing happens in an up market but it usually results in a special assessment that you owe, nowadays it’s a refund. It takes a full year to get the taxes squared away, but it happens automatically and you end up not getting screwed, you pay more or get some back, depending on the scenario.