This is a very difficult question because many of the external signs we look for are not a sufficient a barometer for this. Most people are able to perform the adequate tasks and say the right things that would lead us to some conclusion but the true indicator of love is measured during true hardship when there is nothing in it for them other than grief.
Unless of course, there is something more.
We can blind ourselves to true love and even reject it. We can also convince ourselves that true love exists based on the fair and sunny times we experience with someone which is no sign of their depth of investment. Convincing ourselves that the intensity of our feeling for someone else is being returned with equal fervor, can be tempting but it may be wrong. However it is part of the risk inherent in the great leap we make to find companionship.
For nothing can be more volatile than human emotion and the delicate strings that attach themselves to our individual stories.