well i am sorry to tell you but i think you skipped her.
You see in order to unlock her (so to obtain her number) you have to explore the city at a certain weight stage ( i don't know which one but i guess between 4 and 6) untill you come across a scene in which the protagonist helps Beth at either a part time job or smth like that and in my opinion considering your protagonist weight you could be above that point and just so you know (as far as i know) that event can ONLY trigger at that specific weight stage.
If you want try to use your energy only on go on a walk --> explore city for a few game days and see if you can trigger the event if after (for ex) 7 days you still haven't then you will need to be at a lower weight stage.