<human>: Can you give me the gist of the text in a nutshell?

We've been together three years, married three months. His family invited us to join them on a trip. Our first day there, SO and I decided to have a quickie before dinner. 

We gave his mother a spare key card to our room just in case, but we did not expect her to use it. I guess we were running late for dinner. She came up to see what was taking so long, tried to open the door, unlocked it on her own (even though we put the do not disturb thing up) and caught us. She stared for a second and then ran out embarrassed. My husband and I burst out laughing. He closed the door, we finished ~~because we're monsters~~ and went down to dinner expecting some awkward laughter and a joke or two. 

MIL usually makes the innocent sex joke here and there so we didn't expect her to be traumatized or anything. But she has really made a point to direct weird, shameful remarks at me. Implying I'm a *hussy* for fucking my husband, while conveniently ignoring the fact that she ignored all the signs and unlocked the door on her own. 

SO has tried to talk to her but she "can't look at him". The rest of the family has no idea what happened.
<bot>: on family trip. SO were having sex in our hotel room. MIL has spare key. She unlocked the door and walked in on us. Now she keeps trying to make me feel bad for having sex with my husband.