I can provide some general information that might help you.
In most places, the legal age of consent is 18 years old. Since your girlfriend is 18, there shouldn't be any legal issues with staying together in Oyo rooms in terms of age restrictions.
As for safety, Oyo rooms are a chain of budget hotels and accommodations, and they generally prioritize safety and security for their guests. However, like any other hotel or accommodation, the level of safety can vary depending on the specific location and other factors. It's always a good idea to read reviews and do some research about the specific Oyo room you plan to stay in, to get an idea of the experiences of other guests.
Additionally, since you are both minors (under 18 years old), it's essential to consider whether you have the consent of your parents or legal guardians to stay together in a hotel. Some hotels may have specific policies for minors staying without adult supervision, and it's essential to follow these guidelines.
To ensure a safe and comfortable stay, communicate openly with your parents or guardians about your plans, choose reputable and well-reviewed accommodations, and always prioritize your safety and well-being.
Please note that my information may not be up-to-date, so it's best to check with Oyo rooms directly for their specific policies and guidelines.