18 Month old goes to sleep fine but wakes 2/3 times a night

Hi Everyone!

Our 18 month old daughter was sleep trained but unfortunately things have taken a U-turn in the last few months.

There are no issues in getting her to sleep, she has a solid bedtime routine and nap routine, she usually has only one nap 1.5hrs 11am/12pm, then we start bedtime routine at 6pm (dinner, bath, books) and she’s in bed asleep by 7:30pm/8pm (it’s take her 5/10 mins to go to sleep.

10/11pm she will wake and just want to be in our arms/our bed. We try let her cry (15mins max) and then pat her etc but she still wants to be held, she may eventually fall asleep.

3/4am she will wake again, wanting the same thing, we have a spare bed next to her cot which sometimes after 45mins of trying we will sleep in the bed with her - but this just keeps happening and not sure what to do?

I tried letting her cry for longer but it was really hard emotionally and i think she just keep crying.

Thanks for in advance for any help!