Did you use her as a provider in 2016?  If you did and claimed the expense, her information should be on your 2016 tax return.  You are legally entitled to claim expenses that you paid on your return.

If you cannot get the number and do not have it, you may still claim the expenses, but it likely is going to take more time and likely documentation to do so.  Without the social, you will have to mail your return in, which will take longer to process.  In addition, the IRS can ask for proof of the payments, so you will need to have receipts or cancelled checks.  If you do not have either, it may be difficult to substantiate the claim as you do not have cooperation.  But if you do, you may still be able to claim the expenses.