The W4 has nothing to do with Social Security Tax. It is a mandatory 6.2% on box 3. Each employer holds out the full 6.2%. They don't know if she went over by having another employer. Add up all her box 4. In fact, post the amounts from each W2 box 3&4 so I can check it out.
Yes you get the excess back on your return. It either reduces the tax due or adds to your refund.
If you had more than one employer and the total of box 4 (only box 4 not box 6) on all your 2019 W2s for Social Security is more than $8,239.80 you get the excess back on your tax return. And it is for each spouse separately, not combined. Check 1040 Schedule 3 line 11 for it. Then Schedule 3 goes to 1040 line 18d.
