It seems like we are getting some very heavy foreshadowing that we should be thinking about who is Lift's mom and why she's no longer in the picture. There may be a number of reasons why Lift is so awesome, it seems like it's more than just Cultivation's touch. Perhaps she isn't in the picture anymore because she's a bit unstable? Perhaps she was involved with whatever the mysterious problems are in Ral Elorim? It seems reasonable that Lift's mom could be a herald.
This doesn't preclude Shallan's mom as a herald too. Shallan's extra abilities may be due to her bonding multiple spren and it also involve her lineage.
There isn't any reason to think that radiant abilities are likely to be similar in families. We know that the Davars and Kholins both include multiple orders, but Lift's fond memories of her mother in addition to their shared surges, make me wonder if Vev may be a strong candidate as her mother. What has Vev been up to lately?