That can work. Ness tends to act Mannish when she is among the settlements of the Second Born, just so she doesn't deal with the usual prejudices against her kind. She works as a traveling healer and midwife, though, so she can help Shae out.
Since she becomes Queen of Rohan in 3021, and assuming Shae doesn't kick the bucket by then, they could also meet again in Rohan once she takes up residency there in the Fourth Age. Up until the November before the War (3018), Loth is in Dol Amroth more often than other places, so they could meet there when Loth is young or when she is a preteen or teen. Pretty sure Loth would be star struck as well if she knew Shae was a shapeshifter (and have LOTS of questions concerning it, especially young/lacks-a-lot-of-a-mouth-filter Loth).