Yes, she needs sine rule and cosine rule - not just the basic sine and cosine that they learn first when they do it with right angled triangles, but the more complex rules that are only covered as part of higher tier. If she doesn't recognise those names, then it's possible she hasn't yet done this topic.
If she does recognise it, she will probably know the forumla for each (or they are on a formula she that she may have been given).
a2 = b2 + c^2 - 2bc(cosA). Where A is the angle that she wants to find out, a is the side opposite it, and b and c are the other two sides. She can then rearrange that forumla to make cosA the subject, and then use cos-1 to find A.
Once she has that, and thus the opposite angle, she can then use the sine rule in the smaller triange. This says that side a/sinA = side b/sinB, so she can say that 4/sin A = x/sin60. And then rearrange that equation to get x (the side she is trying to find, AC).
If that doesn't make any sense to her yet, then it's likely that she hasn't done this part of trig yet - if she is trying to do a past paper, then she should probably skip that question for now, until she covers it in class. Sometimes when students are preparing for mocks at this time of year, they haven't yet covered the entire syllabus ,so they need signposting to questions that they might not be able to do yet for valid reasons!
Of course, if it's homework on a topic that she is currently doing, then hopefully she will recognise the rules in that explanation and be able to do it. It is a multi-step question, which can be off-putting at first until students realise what they have to find first in order to use some of the rules.