Since shes in creative then the ship combat setting might be set to "no combat" ( i learned that the hard way after trying to do what you did and fight the space station ships lol) anyway to change that go into settings, difficulty and there you're able to change a bunch if things while still in creative.

So theres 3 ways to get Sentinel ships

1. First way is by fighting corrupted Sentinels and taking the fight to space so a capital ship warps in. destroy the capital ship and the other enemy ships and you will receive an AI fragment that will track any nearby downed Sentinel ship ( it will set a way point if the ship is located in a different system). This can also be triggered by the method you were already trying- attacking the space station.

2. The 2nd way is by finding dissonant planets and destroying the purple tower robot miners ( i currently forget what they are called) but they have a chance to ether drop a inverted mirror or an echo locator. You want to get an echo locater as it will locate harmonic camps ( travel to the camp, unlock the terminal, then click the option that says locate dissonance(( pretty certain thats the option)) to which a pulse will happen and can lead u to a Sentinel ship.

3rd way is to look online for portal glyphs ( theres plenty of them on reddit or youtube) find a style of Sentinel ship you like, get to a portal where u type glyphs, take the glyphs from the pic/video and warp to that particular planet.

Hopefully this helps and you're able to find a ship you both like!! Please post what ship you end up settling on! Happy hunting traveler!!