I don't think they can do this and I suspect only offer to feed this through to those who can over-ride if there are things like children or people with disabilities. If you were AA Emerald then you can use TCP facility instead, otherwise you're essentially asking for a perk reserved for higher tier passengers. If it's more than 72 hours from departure then it's not TS. I'm guessing she has paid for a seat though I can't work out her status from what you've said so far.

If your flight doesn't look like it is going to go out full, then usually between T-72 (when TS kicks in) and T-24 something will come up, then at T24, just don't print your boarding pass and keep checking. TS recomputes massively in this period and I'd very surprised if you can't do anything here to resolve this. Just don't print your boarding pass until the last moment. Depending on the aircraft you can also play around with bassinet selection too. If the cabin is going to be more than full this may be moot anyway, sometimes almost all WTP end up further forward.