Yes, Elizabeth certainly *does* suspect that Mr. Collins might have plans for her. This is from ch.17:

[Elizabeth] was not the better pleased with [Mr. Collins'] gallantry from the idea it suggested of something more. It now first struck her that she was selected from among her sisters as worthy of being the mistress of Hunsford Parsonage, and of assisting to form a quadrille table at Rosings, in the absence of more eligible visitors. The idea soon reached to conviction, as she observed his increasing civilities toward herself, and heard his frequent attempt at a compliment on her wit and vivacity; and though more astonished than gratified herself by this effect of her charms, it was not long before her mother gave her to understand that the probability of their marriage was exceedingly agreeable to her. Elizabeth, however, did not chuse to take the hint, being well aware that a serious dispute must be the consequence of any reply. Mr. Collins might never make the offer, and till he did, it was useless to quarrel about him.