mother in law

So in April my mil came to visit for 6 months from another country. While she may be a nice person I don't find her smart. She's not even 70 yet and acts like an 80 yr old. I feel like the things she says and does cause irritations between my husband and I. I wish she didn't stay for so long but does for immigration reasons. To top it off, we live in a 1 bdrm 1 bath apt. My husband made her sleep in our room and refuses to let her sleep anywhere else. We are ttc #1 and it's not easy and we both are already 38. Sometimes I feel that unintentionally my mil will ruin my marriage. He feels that she is old and shouldn't have any stress in life. Therefore I should do everything from putting her dinner in the plate even if I've just come home from Long days work. Sometimes I lose it and cry out of hopelessness. Anyone have sincere advice