andrei wrote:

She did not say that she did not like paddle - only that she was
getting tired fairly rapidly.

She will get stronger with practice. You could tow her when she
needs a rest (this is what I do with my kids).

It was me who was looking at the paddle change option (since we
cannot change the kayak) in the hope to help her.

A lighter paddle of correct length with a more-ideal feather angle
might help. The $30 Carlisle paddles used to have a choice of only
0 or 90 degree feather, which is terrible. Most experienced paddlers
prefer feather angles somewhere between 45 and 60 degrees. Length
should be sufficient to reach the water on both sides of your boat
without a lot of torso rotation.