My daughter has trouble with the twist shifters on her bike, can you get trigger shifters for a 6 speed? Cheap like.

Triggers here
http://www.ukbikestore.co.uk/product/97/sltx506pa/shimano-sl-tx50-sis-thumb-shifter-plus—6-and-3-speed-pair.html

Or use a 7 speed but index from 6 so there will be a click to 7th but no change.

jonk +1

Be careful with a 7-sp shifter and a 6-sp freewheel or vice-versa.
Spacing is not the same and it will be difficult/impossible to get a good shift across the whole block.

I had this issue with a 6-sp indexed downtube shifter with a 7-sp wheel. It would not index, so I switched back to a 6-sp block.

Friction shift is never a problem, but your daughter may not be capable.

Check it out on Sheldon Brown.

PaulD

having been in the same boat, i’d suggest a good clean and lube on the twisters first, and a nice new cable. If you girl is small she might have trouble with triggers plus they are not as straight forward in function as a twister.

I am sure I have a new 6 speed shifter in the shop. Cheap but ugly though.