silvasands: She will be home for all of the school holidays and it would appear that she intends some flying visits (no thought of her carbon footprints when homesickness takes a grip !).
Hmmm, are you sure you won't be suffering from 'daughtersickness' more than she suffers from homesickness!!
Based on the information supplied it does seem that a Worldwide Annual Multi Trip policy with a longer trip duration limit than standard (just in case she finds herself not coming home as often as she imagines) would be your best bet.
Many policy will limit to 31 or 45 days, if she feels this is sufficient then great if not then you can get some that will go up to more than that. Be careful though some policies do have a maximum duration that you can spend outside the UK during the 12 months that she is insured i.e. 183 days/6 months (unfortunately ours does).
Sorry I cannot recommend any one specific but you may want to start by looking here on MSM to see if they are any policies that meet her requirements.
Best of luck.