I'm an American citizen living in Canada, I have a dependent born abroad but who has her American citizenship through me, but doesn't have a social security number.

I take it she is 12 or older? See "Original Social Security Card". I imagine that you have already been through all this.

As you suspect, you can't add her to a tax return unless she at least has an ITIN, and since you aren't supposed to get an ITIN when you are eligible for an SSN, you are in the Catch-22 situation of you can't use an ITIN because she is eligible for an SSN, but she can't get an SSN because of COVID.

You might try calling the International Taxpayer Service Call Center using the Tel: 267-941-1000 (not toll-free) number (I assume that you can direct dial this from the US). If the SSA can't help you, maybe the IRS has a suggestion on how to resolve the conundrum.