Like netnoy, I have sugar-dated several porn stars. My results vary a bit more widely than his.
But first, let's address your question: What to offer? My suggestion is to start taking her presence on a sugar site at face value - and assume she is looking for a sugar daddy and not escort tricks. Treat her job like it's any other job. There is no reason to call her out for being a sex worker, unless she mentions it. If she really is just looking to find new escort gigs you will see it in her replies and expectations. If she starts asking for an hourly rate, or says "bookings" rather than dates, you can safely reply in kind, if you want to. But otherwise just treat her like any other SB you meet.
When considering an allowance offer, the same negotiation rules and tactics apply. Best if you can get her to make an ask first, then you can properly counter. If not, you will need to make a judgement call. But I suggest you start well below her hourly rate, and always position you offer for a 4-6+ hour date that includes non-BCD as well as BCD time. Sugaring for most is about spending time together doing fun things and building a connection, as well as fucking her brains out.
For my PS experiences, as netnoy, most were short due to flakiness (sometimes fueled by substance abuse), or her finding a bigger wallet that wanted more of her time. But 3 were (and 2 still are) long lasting and very satisfying arrangements. This includes my last 6-hour BCD 2 days ago with my A-List Asian porn star. I'm still tingling from her begging Daddy to spank her naughty behind until she came (and she DID). She made me video it as well - for my personal use. And her allowance: less than half her hourly escort rate.
Of the other 2 arrangements, one retired from the industry and got married. The other is now on my B-Rotation as she moved about 2 hours away. She does not escort, but my sense is her allowance is about 40% of what she gets paid for a porn shoot.
The main takeaway here is this: Treat her like any other "civilian" POT, unless and until she asks to be treated as a hooker.
Life is good
The Cat