Desmond Scott’s ex Marissa Springer is spilling on their whirlwind fling … and says from the jump, he was throwing some serious money at her and spoiling her like it was no big deal.

Marissa sat down with TMZ’s Charlie Neff and told us things escalated fast … claiming the very next day after we broke the clip of their steamy make-out session, he handed over his credit card and told her to go wild.

Check the clip — she breaks down exactly what she bought and whether she hit the $25K limit he gave her — but now says it all feels a little different in hindsight. Marissa suspects the shopping spree may have been hush money, especially since he was in the middle of a very public split from his wife Kristy Scott … and didn’t even show up for the spree himself.

She also weighed in on our story about Desmond now dating one of Diddy‘s former partners, Dana Tran — saying the pairing feels off. Still, Marissa admits his phone lit up with Dana’s name while they were together … she just didn’t notice it at the time.

And if Desmond’s watching? Marissa’s got a warning — be careful, ’cause Diddy could be out of jail soon!!! Pretty intense stuff from our sit-down … catch the full interview on YouTube.

As for Desmond’s side, sources close to him tell TMZ he only bought Marissa a single purse worth $3,788.75 — and insist there was nothing to hush, since the two were already done.