In few months I will be traveling to Russia to visit my gf there. I will be booking a Hotel just for myself, will the staff/reception/security have any issues with letting my gf get into the Hotel during the day/evening? How does this work or do you have any advice please?
PS: She wouldn't be able to sleep over otherwise I would have booked for two people.
There's scant documentation on the net about it, but generally your gf will have a very difficult time getting by the concierge or hotel security. It's likely she will not be successful because they like to keep a close eye on such things. It's likely your gf would be aware of the situation in the first instance.
If she somehow manages to get past the lobby security, there's still secondary security on each floor supported by cameras (especially in the larger hotels). What this amalgamates to is: they don't like it and they are watching for it. They don't care if she's not 'sleeping over'. They don't care if she's your gf in a serious relationship. It's just the way things work.
If she gets caught sneaking in, she'll have the option of paying off hotel security or paying off the police when they show up. Things can get ugly fairly quickly.
The problem is soliciting and prostitution (and secondarily, the opportunity for staff to supplement their income). You can skirt the issue in one of two ways:
I always opted for the latter because it seemed more economical (and more chivalrous). You did not mention the locale, my answer is relevant for Moscow, Peter, Samara, and Stavropol. Probably you can find exceptions, but they would hardly be 'tourist' quality. Hotels in the more remote regions (Perm, Tomsk, Krasnojarsk for example) may have different principles, but I doubt it.
Adding...
A prostitute working the hotel lobby or bar isn't included in this answer. These girls have on-going arrangements with hotel staff and can go to your room without challenge. Various comments on Trip Advisor like this one, dated 2010: http://www.tripadvisor.co.uk/ShowUserReviews-g298518-d1200684-r77686812-Amaks_Tourist_Hotel-Ufa_Republic_of_Bashkortostan_Volga_District.html,
Trip report from Peter in 2012: http://www.travelpod.com/hotel/Moscow-Hotel-St_Petersburg.html
Trip report from Moscow dated 2014: http://www.tripadvisor.co.uk/Hotel_Review-g298484-d299980-Reviews-Hotel_Cosmos-Moscow_Central_Russia.html#REVIEWS
The 'golden solution' is to get a furnished flat and dispense with hotel complications altogether. They can be surprisingly economical.
Finally, you can consult a forum largely devoted to men visiting their girlfriends in Russia. There are enough current threads such as What are hotels like in the FSU, where people are giving first hand anecdotes of experiences and impressions...
See also Russian Law: 25.04.1997 № 490, Federal Law of the Russian Federation for the legislation from which hotel operators derive the right to set guest policies.
It depends on where exactly you are going to stay. In big cities, especially in international network hotels, it is not a problem at all. I've actually had travelled a lot in Russia - and disagree with @Gayot Fow (actually, to be honest, this answer surprised me a lot, I've lived in hotels in Russia pretty often), this is not the case in Moscow and Saint Petersburg.
In a shitty hotels in relatively small towns - unfortunately this can happen. Well, I can advise you just not to stay in such hotels at all. The other thing is that unfortunately it is not always an option.
Also, it worth to mention that if you have two-bed room this would be something very, very strange if you won't be allowed to live with your girlfriend. Say, one had paid for beakfast and the other one does not. That's it.
British and lived in Moscow fifteen years but stay in Hotels all over Russia and often. How often? Three hundred days in a year is my record (Business).
Situation (Moscow) has changed since the late 90's when you'd only not be bothered in the Savoy, Kempinski, National... nowadays even the budget hotels don't give a damn.
So unlikely you will be bothered to be honest.
At most you'll be shaken down at the cheapo hotels (and mostly outside of Moscow) for a few hundred rubles but even that would surprise me.
Prostitutes in the lobby? Perhaps ten years ago and certainly at the tourist hotels (the old Rossiya/Moskva /Intourist, all three demolished and kind of rebuilt) twenty years ago. Now mostly a thing of the past.
@GayotFow I don't read hotel policy documents beyond those related to my reward cards points I'm afraid but I have likely stayed in more hotels in Russia than 99.99% of people :) Actually make that 99.999%.
@OliverMGrech have a good trip!
