Please I need advice read below and give your opinion thanks!?

I left Nigeria 15 years ago and presently reside in London. Before leaving Lagos Nigeria I use to work in an office and I knew a lady colleague whom I use to tell all my problems and worries at that time as I use to chat too about my private life to her but I realized that she never use to tell me anything about herself which I believe is normal. I discussed this with my husband of recent and he told me that wherever you work you should never make friends in an office. I also realised to make friends with someone it takes several years to understand someone before they can become your friend as it is not because you meet someone of new and chat with them that they are your friends. I as an African noticed during my years in Nigeria people tend to chat with some people they do not know very well but later they drifat apart. As I am much older and wiser I study individuals and try not to chat too much with a person on the first day as I realised that it is not because you chat with them that they are nice people. Two weeks ago I received facebook email from my lady colleague of 15 years ago to whom I replied. I replied her via email and exchanged telephone numbers and email addresses but I was not very excited nor enthusiastic. At present I am not very enthusiastic about her nor am I keen on seeing her because it has been 15 years ago I saw her last. I would like to know is this normal. Oneday she telephone me as I politely told her not to phone me as it is expensive that we could communicate via email to which she agreed. As I know people in tropical countries like to chat too much on the phone. Last week I checked my voicemail and listened to her message as she wanted to know how I was doing. Several days later I returned her call and during our discussion I noticed she really did not have much to discuss with me as I was the one doing all the talking resulting to wasting my spare change. As I will be travelling to Lagos I will be forced to pay her a visit. I asked her if I could come to visit her in her office to which replied "yes". As I would be staying in a hotel I would like to know Should I invite her for lunch. I would not like to her ask her if I can come to her house unless she invites me as it her privacy. On meeting her should I talk less about myself? Should I watch her body language to know if she is feeling comfortable with me? She claims she is my friend but I know she is not a friend but a colleague. Tell me? Someone you have forgotten about after 15 years agos are they still your friend old acquaintances or platonic people.