300 Lbs client, I need serious advice !

I need your advice,
My client is a 26 years old graduate, She is 167 Cm (5.4 Ft) - 136KG (299 lbs).

What i like about her is her determination and mind set, it was not easy for her to show up to my bootcamp as she was very shy...
now she wants to come on regular bases... but I can see that my bootcamp will not benefit her as much (too intense for her) as If i gave her a one-on-one sessions at this stage (I will do it for free as I do not think she can afford me).. so:

She does not have any medical condition, she said that the weight was gained due to medication last year which she stopped.
putting her on a HiiT program of 30 sec hi intensity and 2-3 min low intensity would do the trick right? but I still do not want to risk any injury to joints or ligaments.

I am not sure where to start with her, what would be a good approach to get her on track ?

PS. stationary Bikes are out of question, wont be comfortable at this stage!

Pls advice!