Complete treatment for Squint is below 10 yrs old,below 10 yrs if child  undergoes for pleoptic treatment for improving vision in amblyopic eye, it takes 1 to 6 months depending on severity of  amblyopia,now you are 18 yrs old so only cosmetic correction is possible which will again take anatomical position in5-10yrs (divergent squint) but if in childhood you would have gone for Squint surgery after pleoptic treatment ,it would not have developed Squint again in life & would have got binocular vision for ever.

Squint can be corrected for cosmetic reasons. Poor vision in that eye may not improve much as after 14 yrs of age the brain centre for vision is not responsive..

No need to get disheartened. there is treatment for squint and vision improvement will depend on wether she has refractive error and how much is it .Will need to evaluate the squint properly before undergoing any treatment.