If I make it with Thane in the hospital, will that hurt my chances of getting back with Liara?

In Mass Effect 1, I got dirty with Liara. In Mass Effect 2, for lack of any better options, I bumped uglies with Thane. (Really, the choices for Femshep weren't that great in ME2.) Now, Mass Effect 3 is here and although I told Liara that things are over between Thane and myself, I've run into Thane in the hospital, and may have "accidentally" clicked the paragon option to kiss Thane and then again "accidentally" clicked the dialog choice telling him to "take me to bed or lose me forever." Don't judge! It's the end of the world as we know it -- that should be free license to sleep around!

Anyway, will my little fling with Thane prevent me from getting jiggy with Liara again?

(In truth, I'd rather tango with Traynor, but I don't know if that would count towards the paramour achievement.)

Solution 1:

Handling your concerns in order:

Liara will be suspicious of you if you go back to Thane, and relations between you will cool for a while, but eventually, events will conspire to end that relationship permanently. At that point, Liara will be open to taking you back.

Traynor also does count for the Paramour achievement however, so if you'd prefer to go that route, you'll need to cool it down with Liara fast. The game seems to lock you in to a romantic path fairly early on.