I have the echo-e single bottom coil carts now and they work pretty good on an ego battery . Not like a dual or LR cart but since she is just starting out and didn't do well with the 510-T and the 24 mg/ml juice I have gotten her a couple of echo-e carts and Smok 510-T and carts and also have 3ohm boge cartos on the way . I will be starting her out on 9 mg/ml juice . That souldn't give her a sore through that see complained about with the 24mg/ml juice . I'll start her out slow and go from there .
I was vaping 8 mg for a while and still got a sore throat yet so it may not be the nicotine. First she needs to drink plenty of water when vaping as both PG and VG are hygroscopic and will dry out the back of her throat. I can't tell you if a higher blend of VG will hope but that is what I'm trying next. So far I have only had the Chinese jooses that are 100% PG and am hoping that a 20-30% VG blend will help.
Drinking more water definitely helps though!