A couple things. I'm a 'grandma' myself (but I think of myself as 'modern' LOL). Anyway, I'm a 'do-it-yourselfer' (although I am married for almost 33 years) and I used to take the flat part of a thumb- or fingernail and rub on a tooth that I could feel ready to erupt. You say you don't feel the bumps nor even swelling, so if she's chewing on everything already & it isn't bringing anything through, maybe there's nothing ther to BRING through. I don't understand the pain, so it would probably be prudent to schedule a visit w/a Ped. dentist (call around first and ask prices for a 'preliminary check-up' unless you have good dental insurance). Also, metal thimbles used to just have little 'dips' in them (like a golf ball has, but smaller, of course), but now they're way more ridgy and rough, so I'd just go with the flat of the fingernail thing or just something hard and smooth (and even cool, like a thick, smooth case-knife handle), but be careful not to bruise, because you really DO have to apply some pressure. Even with the fingernail there's the chance that your finger will slip and cut the gum. Hope you can get her some relief!
Might her discomfort even be caused by something ELSE??
God bless!