There are more details needed to give you a complete response. In general, Alimony can be items that are paid for on behalf of the ex-spouse under certain conditions, and those items could be deductible. For example, if an item (or cash) is not considered child support and the divorce decree doesn't say it's "not" alimony it could be claimed. This may be why you were told by someone else that you can claim the car payments.
That said, if the car payment was not part of the divorce settlement, it is not deductible at all.
Also, if the car is in your name (you are the owner of record), then you are paying to keep up property you own and it's not deductible in that case either.
The other main concern is whether or not all items in the divorce decree state that they are to be stopped upon her remarriage. In that case, the car payment again would not be deductible, even if it was considered "alimony".
This link has more details if you want to check it out IRS Pub 504 Divorced or
Separated Individuals .