In all honesty I think she needs to try the cues, is there a pool/snooker shop close to you? £40-£50 can get an ok cue but you could also spend that on a "brand" cue and get something useless. Cues can be so diffrent that unless she knows the type she wants your just as likely to get something naff. (tip size, length, weight, 1/2 3/4 full length etc)
Got mine custom made for £180 but Steven Hendry won more than a few tournys with a £7.99 cue.