Most 3 star hotels will let them in but they'll need to produce their ID card. Like our friend said get an airbnb that'll get around that problem. Or get friendly with the doorman at the hotel slip him a few dong and he'll slip her up the stairs unseen. Just a word of warning that some girls will take the opportunity to pick up a few souvenirs so make sure any valuable items are out of sight and locked away. I have been a victim of the " you take a shower first" trick and as soon as they hear the water running they go for your valuables.