Do you think this relationship will work?

I know this women well really a girl she is only 18 and she is seeing an older man. I dont mean older as in 10 or 15 years but he is 50 years old. I know the age is a huge gap but they seem very happy and they bring out the best in each other. I have never seen her so happy in my life and it seems that she is starting to turn her life around and becoming a mature women but i wonder if this relationship is healthy for her age and what may happen to her/them in the future. Also they have been seeing each other for about 3 months now and they have not done anything ual yet so its not like he is using her for that. What do you think about this relationship and where do you see them in 5 years from now and is this relationship healthy for the two of them? Please help me with this!!! ooo yes also they say they r in love with each other and would love to get married and have a family!!!