The player doesn't go bust on the second hit if she draws a pair of cards that sum to $5$ or less. All cards up to $5$ are still in the deck. The admissible pairs are $(A,A)$, $(A,2)$, $(A,3)$, $(A,4)$, $(2,2)$, and $(2,3)$, which is $2$ pairs of equal ranks of which there are $\binom42=6$ each and $4$ pairs of different ranks of which there are $4^2=16$ each, for a total of $2\cdot6+4\cdot16=76$ pairs out of $\binom{48}2=1128$, so the probability is $\frac{76}{1128}=\frac{19}{282}\approx6.7\%$.