I've done this many times in many IHG hotels and never had an issue. To be sure I usually send an email to the hotel after booking to inform them that we are travelling separately and my partner is arriving first, and I will be joining her very late that evening. This at least gives something of a pretence that I'm coming in case they are funny about it, and provides them an opportunity to inform me in advance if they will need to see my ID or anything when I check in, which has never been the case. Probably more pantomime than is needed, however I'm also ensuring she gets the perks from my RA status which the hotels are usually more strict about ensuring the person with the status is present.