My daughter just had a tongue tie release surgery, and the doctor put stitches. what will happen next? what should she eat/do? she says it hurts.

Go see surgeon: Any time someone has (or plans to have) surgery, it's best to ask surgeon what will happen next, what to eat/do, what to expect/do for pain, what bad signs need to reported immediately, etc. Clarify all this prior to surgery during the pre-op session. Surgeon can also explain what kind of stitches will be used eg dissolving or non-dissolving and when stitches need to come out (if they do).

Get better: Usually stitches resolve and absorbed. Your child may have some discomfort, but it is short lived. Call the doctor for pain medications or eval. If it is not resolved.

Should get better: Ask your surgeon if there are specific questions. Generally a little oragel numbing gel under the tongue as needed can help, as can tylenol (acetaminophen) alternated with ibuprofen. The stitches are likely absorbable and will "pop" out over the next 2-7 days. If they pop sooner and leave a gap, don't worry. It will look white-yellow for the next week or so which is normal. Then it should return to normal.