N.W.
For my daughter (3) she initially liked to go back and forth as it took some time get the new way of peddeling. Now 3 months later she usually only wants to ride her bike. This also because all the other little girls in the neighborhood all have bikes and they hang together.
I wouldn't worry it is just an adjustment period having both isn't going to confuse her or prevent her from eventually using the bike full time.
Best of luck.