There is insufficient information. We need to know the height of the mirror or the distance between Stacy's eyes and the top of her head. If we assume that the top of her head is 4" above her eyes (Stacy is 5'4" tall) and the top of the tower appears to be just visible at the top of her head in her reflection, we can work out how far away the tower is using similar triangles:
(Stacy's height less 5')/16=(Height of tower less 5')/(distance d of tower from mirror+8').
I'll explain the equation in more detail in a minute.
(1/3)/16=95/(d+8); 1/48=95/(d+8), d=48*95-8=4552' at most.
EXPLANATION
Consider the mirror as a screen behind which the reflection is a real world. Stacy's reflection will be 16' away from her, because she is 8' in front of the mirror so her reflection is 8' behind it. The tower is 8' more than d because Stacy is standing 8' away from the mirror making the tower's reflection d+8 feet away. Everything must be measured from eye level, because the angle of elevation of the top of the tower is the same as that for the top of Stacy's head in her reflection. The position of Stacy's eyes above the ground is important because all vertical measurements must be calculated from eye level. Hence the reason for deduction of 5' from the heights of the tower and Stacy herself. 4" is 1/3'. 4552' is the maximum distance, because if the tower were further away, Stacy's reflection would obscure it.
If the height of the top of the mirror from the ground is known, the top of the tower will only be visible as long as its reflection can be seen. In this case the angle of elevation will be different: (height of top of the mirror, h, above the ground less 5')/8=95/(d+8). If h=6' then 1/8=95/(d+8), d=8*95-8=752' at least. If the tower were nearer the top would not be visible in the mirror.