Need some potty training help

I have a 3.5 Month old Rough Collie pup, she is an amazing puppy and is very well behaved for being a puppy. The biggest flaw of hers is that she will only go potty inside if she isn't let out with other dogs. I take her out every 90ish minutes and she just won't go, but if other dogs are out she will go just fine. And it's not random spots either through the house it's one spot in each room so we know whenever she's back there sniffing it's time to go out but I take her out and nothing. Any advice is greatly appreciated