Put another way, if I'm evaluating an investment and the company will not share this information it makes my decision easy: walk away.
This is not to say you need to provide it early in the process. You could agree to provide the information prior to closing with the understanding that if the investor does not like what they see they are likely to withdraw.
Bottom line: showing respect for your current investors is good; refusing reasonable requests from prospective investors is self-defeating.
By the way, does the angel wish to sell? If they don't know this is under consideration you should bring them into the discussion. There are financial, tax and personal/emotional implications you may need to consider including the potential loss of section 1202 tax benefits if the position has not been held for at least five years.