Sounds like she might have fallen asleep- it's hard to tell for sure with most snakes* & I agree it's unusual for a new snake to be so relaxed, but maybe you have a good snake vibe- plus just the right warmth for a still-digesting boa.(*Snakes with round pupils- you can tell they're asleep if their pupils sink to the 6 o'clock position. Vertical pupils, you're outa luck.) I like it when my snakes really relax with me like that. Just be careful when some of them wake up though, lol. Predators being startled awake can react defensively- especially if it's never happened to them before.
Snakes are rarely constipated- they only go when they've saved up enough waste to bother- remember their bodies need to conserve water, & defecation uses (wastes) some moisture. Also, young snakes that are eating young prey are digesting MOST of what they've eaten- only when they're eating more mature prey is there more waste, so very often young snakes go less frequently- this gets asked a lot.Snakes seldom "go" after every meal.