Yes.

Because L established overlap to leeward from clear astern within two boatlengths of W, L may not sail above her proper course (rule 17). Also, because W was clear ahead when she reached the zone, L must give W mark-room (rule 18.2(b)).

So, as they approach the mark, L may not luff-up, and she must allow W to sail to the mark. When they reach the starboard-tack layline, however, L's proper course (the course she would sail in the absence of L) is to tack. Also, L's tacking would not prevent W from rounding the mark. Therefore, neither rule 17 nor rule 18.2(b) prevents L from tacking.

Rule 13 though, would kick in the moment L passed head-to-wind. L is free to turn head-to-wind provided she gives W room to keep clear (per rule 16.1). If W wishes, however, she may prevent L from tacking by placing herself in a position where L would be unable to keep clear after passing head-to-wind.

As a practical matter, W most likely would (and in this scenario did) tack. If W's goal is to extend her lead on L, then she can hold L at head-to-wind until L loses headway and then tack.

I hope that helps,
Eric