"...my rational mind is telling me lymphoma would not show symptoms of coming and going, correct??"
Yes, very very correct :)
"...she has been putting the antibiotic/steroid cream that was given to her while we visited the doctor overseas, and it's much much better."
That is a point of interest. Write down on your phone or somewhere the exact name of that med, and tell each of the upcoming 2 docs about how well it worked. Always have some of that creme on hand, too. This is unfortunately likely to keep repeating until the underlying cause (hyper immune reaction) is corrected.
We don't know at this point if it was the antibiotic or the anti-inflammatory that did the trick. I'd guess the latter.
No, it's not lymphoma. Cancer doesn't "behave" like that, popping up overnight then simply going away. Chances of lymphoma are just about zero.
But I wouldn't just forget about it. Her immune system reaction was unusually strong. So she'll probably have unusual and mysterious reactions from time to time throughout life. It probably has also been in her past. When it does happen again in any way, think "her immune system is doing something not-average". You'd also look for the same in closely related family members, possibly including yourself. And btw, from what I've seen, hyper reactive immune systems are also associated with anxiety as well.
Docs at ERs and walk-ins won't think along those lines, and they can't be expected to since that's not their field. They are anyway mostly concerned about "is this dangerous", not about the "why". However, there are "functional medicine doctors" who do try to figure out the why of things.